Information-signal recording and reproducing apparatus

ABSTRACT

A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp. The predetermined constant transfer rate Rp, the first transfer rate Ra, the second transfer rate Rb, the size Ya of the first information signal, the size Yb of the second information signal, a seek time Tab taken by the head to move from the first area to the second area of the recording medium, and a seek time Tba taken by the head to move from the second area to the first area of the recording medium are in a relation as follows:  
     ( Ya+Yb )≧ Rp ·( Ra+Rb )·( Tab+Tba )/( Rp−Ra−Rb )

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to an information-signal recordingapparatus and an information-signal reproducing apparatus. Also, thisinvention relates to an information-signal recording and reproducingapparatus. In addition, this invention relates to an information-signalcommunication apparatus. Furthermore, this invention relates to aninformation-signal recording medium.

[0003] 2. Description of the Related Art

[0004] A typical optical-disc recorder/player operates as follows.

[0005] During a recording mode of operation of the recorder/player, asignal representing at least one of video information and audioinformation is compressed into a compression-resultant informationsignal. An optical head in the recorder/player records thecompression-resultant information signal on an optical disc. During aplayback mode of operation of the recorder/player, the optical headreproduces a recorded signal from an optical disc. The reproduced signalis expanded into an original information signal.

[0006] It is known to provide such an optical-disc recorder/player witha buffer memory having a capacity of about 4 Mbits. A recorded signal isreproduced from an optical disc at a transfer rate of 10.08 Mbps. Thereproduced signal is converted into an information signal having avariable transfer rate lower than 10.08 Mbps. The buffer memory absorbsthe difference in transfer rate between the before-conversion signal andthe after-conversion signal.

[0007] Japanese published unexamined patent application 10-92158discloses a disc reproducing apparatus designed as follows.Discontinuation and disturbance of an image are prevented by dividing acell into a plurality of cells, time-division-multiplexing the cells ineach scene and arranging and recording the cells to be reproducedcontinuously within the distance of the particular amount of codes toshorten the physical moving distance during the reproducing operation.In Japanese application 10-92158, a video program has a preceding fronttrunk scene A, a plurality of branch scenes B0 to B3, and a successiverear trunk scene C. In the case of recording a plurality of branchscenes on a recording medium, any branch scene is arranged in such amanner that a scene cell appears in the same rate for the summed totalscene length. Arrangement should be done so that when the time forjumping the distance for the amount of particular codes is defined asTs, the relationship Tc−[Tc×Pr/Rr]>Ts can be set for the amount ofreadout data Rr, amount of codes consumed Pr and image reproducing timeTc. When arrangement for recording is performed, a physical movingdistance during the reproducing operation can be shortened andgeneration of discontinuation and disturbance of image can be prevented.The branch scenes B0 to B3 are multiple scenes. Each of the branchscenes B0 to B3 has a sequence of cells. The cells of the branch scenesB0 to B3 are shuffled before being recorded on a disc (a recordingmedium). Thus, the recorded cells of the branch scenes B0 to B3 are onnon-successive separate positions on the disc. Accordingly, during thereproduction of the sequence of cells of one branch scene, a pickup headreproduces the cells and repetitively jumps between non-successiveseparate positions on the disc. In the apparatus of Japanese application10-92158 includes a buffer memory capable of absorbing a time intervalduring which a pickup head jumps between non-successive separatepositions on the disc so that reproduced data continue to be absent.Japanese application 10-92158 indicates the relation between thecapacity of the buffer memory and a seek time of the pickup head whichenables the buffer memory to continuously output data under conditionswhere the pickup head reproduces a sequence of cells of one branch sceneand repetitively jumps between non-successive separate positions on thedisc.

[0008] Japanese published unexamined patent application 6-139696discloses a recording and reproducing apparatus which includes a buffermemory for absorbing a difference between transfer rates. In Japaneseapplication 6-139696, during a recording mode of operation of theapparatus, first digital data having a lower transfer rate and beingderived from an information signal to be recorded is converted intosecond digital data with a higher transfer rate. The second digital dataare recorded on a disc at the higher transfer rate. During a playbackmode of operation of the apparatus, third digital data are reproducedfrom the disc at the higher transfer rate, and the reproduced digitaldata are converted into fourth digital data related to the lowertransfer rate. The fourth digital signal is converted into a reproducedinformation signal. The recording mode of operation and the playbackmode of operation are implemented on a time sharing basis so that theinformation signal to be recorded and the reproduced information signalcan simultaneously occur.

SUMMARY OF THE INVENTION

[0009] It is a first object of this invention to provide an improvedinformation-signal recording apparatus.

[0010] It is a second object of this invention to provide an improvedinformation-signal reproducing apparatus.

[0011] It is a third object of this invention to provide an improvedinformation-signal recording and reproducing apparatus.

[0012] It is a fourth object of this invention to provide an improvedinformation-signal communication apparatus.

[0013] It is a fifth object of this invention to provide an improvedinformation-signal recording medium.

[0014] A first aspect of this invention provides an apparatus forreproducing information from a recording medium having first and secondareas on which first and second information signals are recordedrespectively, the first information signal having a size Ya, the secondinformation signal having a size Yb. The apparatus comprises a head forreproducing the first and second information signals from the first andsecond areas of the recording medium and transmitting the reproducedfirst and second information signals on a time sharing basis and at apredetermined constant transfer rate Rp while moving between the firstand second areas of the recording medium; and a buffer memory forreceiving the first and second information signals from the head at thepredetermined constant transfer rate Rp, for temporarily storing thefirst and second information signals, and for outputting the first andsecond information signals at first and second transfer rates Ra and Rbrespectively, the first and second transfer rates Ra and Rb being lowerthan the predetermined constant transfer rate Rp; wherein thepredetermined constant transfer rate Rp, the first transfer rate Ra forthe first information signal, the second transfer rate Rb for the secondinformation signal, the size Ya of the first information signal, thesize Yb of the second information signal, a seek time Tab taken by thehead to move from the first area to the second area of the recordingmedium, and a seek time Tba taken by the head to move from the secondarea to the first area of the recording medium are in a relation asfollows:

(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)

[0015] A second aspect of this invention provides an apparatus forrecording information on a recording medium having first and secondareas. The apparatus comprises a buffer memory for receiving first andsecond information signals at first and second transfer rates Ra and Rbrespectively, for temporarily storing the first and second informationsignals, and for outputting the first and second information signals ata predetermined constant transfer rate Rp higher than the first andsecond transfer rates Ra and Rb, the first information signal having asize Ya, the second information signal having a size Yb; and a head forreceiving the first and second information signals from the buffermemory, and for recording the first and second information signals onthe first and second areas of the recording medium respectively on atime sharing basis and at the predetermined constant transfer rate Rpwhile moving between the first and second areas of the recording medium;wherein the predetermined constant transfer rate Rp, the first transferrate Ra for the first information signal, the second transfer rate Rbfor the second information signal, the size Ya of the first informationsignal, the size Yb of the second information signal, a seek time Tabtaken by the head to move from the first area to the second area of therecording medium, and a seek time Tba taken by the head to move from thesecond area to the first area of the recording medium are in a relationas follows:

(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)

[0016] A third aspect of this invention provides an apparatus forrecording and reproducing information on and from a recording mediumhaving first and second areas, the first area being loaded with a firstinformation signal having a size Ya. The apparatus comprises a head forreproducing the first information signal from the first area of therecording medium and transmitting the reproduced first informationsignal at a predetermined constant transfer rate Rp; and a buffer memoryfor receiving the first information signal from the head at thepredetermined constant transfer rate Rp, for temporarily storing thefirst information signal, and for outputting the first informationsignal at a first transfer rate Ra lower than the predetermined constanttransfer rate Rp; the buffer memory being for receiving a secondinformation signal at a second transfer rate Rb lower than thepredetermined constant transfer rate Rp, for temporarily storing thesecond information signal, and for outputting the second informationsignal at the predetermined constant transfer rate Rp, the secondinformation signal having a size Yb; the head being for receiving thesecond information signal from the buffer memory, and for recording thesecond information signal on the second area of the recording medium atthe predetermined constant transfer rate Rp; wherein the head implementsreproduction of the first information signal from the first area of therecording medium and recording of the second information signal on thesecond area of the recording medium on a time sharing basis while movingbetween the first and second areas of the recording medium; and whereinthe predetermined constant transfer rate Rp, the first transfer rate Rafor the first information signal, the second transfer rate Rb for thesecond information signal, the size Ya of the first information signal,the size Yb of the second information signal, a seek time Tab taken bythe head to move from the first area to the second area of the recordingmedium, and a seek time Tba taken by the head to move from the secondarea to the first area of the recording medium are in a relation asfollows:

(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)

[0017] A fourth aspect of this invention provides an apparatus forreproducing information from a recording medium having first and secondareas on which first and second information signals are recordedrespectively. The apparatus comprises a head for reproducing the firstand second information signals from the first and second areas of therecording medium and transmitting the reproduced first and secondinformation signals on a time sharing basis and at a predeterminedconstant transfer rate Rp while moving between the first and secondareas of the recording medium; and a buffer memory for receiving thefirst and second information signals from the head at the predeterminedconstant transfer rate Rp, for temporarily storing the first and secondinformation signals, and for outputting the first and second informationsignals at first and second transfer rates Ra and Rb respectively, thefirst and second transfer rates Ra and Rb being lower than thepredetermined constant transfer rate Rp, the buffer memory having acapacity Ym; wherein the predetermined constant transfer rate Rp, thefirst transfer rate Ra for the first information signal, the secondtransfer rate Rb for the second information signal, the capacity Ym ofthe buffer memory, a seek time Tab taken by the head to move from thefirst area to the second area of the recording medium, and a seek timeTba taken by the head to move from the second area to the first area ofthe recording medium are in a relation as follows:

Ym>{(Rp−Ra)·Ra+(Rp−Rb)·Rb}·(Tab+Tba)/(Rp−Ra−Rb)

[0018] A fifth aspect of this invention provides an apparatus forrecording information on a recording medium having first and secondareas. The apparatus comprises a buffer memory for receiving first andsecond information signals at first and second transfer rates Ra and Rbrespectively, for temporarily storing the first and second informationsignals, and for outputting the first and second information signals ata predetermined constant transfer rate Rp higher than the first andsecond transfer rates Ra and Rb, the buffer memory having a capacity Ym;and a head for receiving the first and second information signals fromthe buffer memory, and for recording the first and second informationsignals on the first and second areas of the recording mediumrespectively on a time sharing basis and at the predetermined constanttransfer rate Rp while moving between the first and second areas of therecording medium; wherein the predetermined constant transfer rate Rp,the first transfer rate Ra for the first information signal, the secondtransfer rate Rb for the second information signal, the capacity Ym ofthe buffer memory, a seek time Tab taken by the head to move from thefirst area to the second area of the recording medium, and a seek timeTba taken by the head to move from the second area to the first area ofthe recording medium are in a relation as follows:

Ym>{(Rp−Ra)·Ra+(Rp−Rb)·Rb}·(Tab+Tba)/(Rp−Ra−Rb)

[0019] A sixth aspect of this invention provides an apparatus forrecording and reproducing information on and from a recording mediumhaving first and second areas, the first area being loaded with a firstinformation signal. The apparatus comprises a head for reproducing thefirst information signal from the first area of the recording medium andtransmitting the reproduced first information signal at a predeterminedconstant transfer rate Rp; and a buffer memory for receiving the firstinformation signal from the head at the predetermined constant transferrate Rp, for temporarily storing the first information signal, and foroutputting the first information signal at a first transfer rate Ralower than the predetermined constant transfer rate Rp, the buffermemory having a capacity Ym; the buffer memory being for receiving asecond information signal at a second transfer rate Rb lower than thepredetermined constant transfer rate Rp, for temporarily storing thesecond information signal, and for outputting the second informationsignal at the predetermined constant transfer rate Rp;

[0020] the head being for receiving the second information signal fromthe buffer memory, and for recording the second information signal onthe second area of the recording medium at the predetermined constanttransfer rate Rp; wherein the head implements reproduction of the firstinformation signal from the first area of the recording medium andrecording of the second information signal on the second area of therecording medium on a time sharing basis while moving between the firstand second areas of the recording medium; and wherein the predeterminedconstant transfer rate Rp, the first transfer rate Ra for the firstinformation signal, the second transfer rate Rb for the secondinformation signal, the capacity Ym of the buffer memory, a seek timeTab taken by the head to move from the first area to the second area ofthe recording medium, and a seek time Tba taken by the head to move fromthe second area to the first area of the recording medium are in arelation as follows:

Ym>{(Rp−Ra)·Ra+(Rp−Rb)·Rb}·(Tab+Tba)/(Rp−Ra−Rb)

[0021] A seventh aspect of this invention is based on the first aspectthereof, and provides an apparatus further comprising means forpartitioning the buffer memory into first and second areas in accordancewith values of the first and second transfer rates Ra and Rb, whereinthe first and second areas in the buffer memory are assigned to thefirst and second information signals respectively.

[0022] An eighth aspect of this invention is based on the first aspectthereof, and provides an apparatus further comprising means forpartitioning the buffer memory into first and second areas in accordancewith an operation mode, wherein the first and second areas in the buffermemory are assigned to the first and second information signalsrespectively.

[0023] A ninth aspect of this invention is based on the first aspectthereof, and provides an apparatus further comprising a first unitcontaining the head, and a second unit detachably connected with thefirst unit and containing the buffer memory.

[0024] A tenth aspect of this invention provides an apparatus comprisinga head for reproducing an information signal from a recording medium andtransmitting the reproduced information signal at a predeterminedconstant transfer rate; a buffer memory for receiving the informationsignal from the head at the predetermined constant transfer rate, fortemporarily storing the information signal, and for outputting theinformation signal at a transfer rate lower than the predeterminedconstant transfer rate; a processor for receiving the information signalfrom the buffer memory and subjecting the information signal to areproducing process; a first unit containing the head; and a second unitdetachably connected with the first unit and containing the buffermemory and the processor.

[0025] An eleventh aspect of this invention provides aninformation-signal communication apparatus comprising the apparatus ofthe fist aspect of this invention and an interface connected with thebuffer memory for communication with an external.

[0026] A twelfth aspect of this invention is based on the eleventhaspect thereof, and provides an information-signal communicationapparatus further comprising a first unit containing the head, and asecond unit detachably connected with the first unit and the interfaceand containing the buffer memory.

[0027] A thirteenth aspect of this invention provides aninformation-signal recording medium having first and second areas onwhich first and second information signals are recorded respectively,the first information signal having a size Ya, the second informationsignal having a size Yb, wherein the first and second informationsignals can be reproduced from the first and second areas and can betransmitted by a head on a time sharing basis and at a predeterminedconstant transfer rate Rp while the head moves between the first andsecond areas of the recording medium, wherein the first and secondinformation signals outputted from the head can be received by a buffermemory at the predetermined constant transfer rate Rp and can betemporarily stored in the buffer memory before being outputted from thebuffer memory at first and second transfer rates Ra and Rb respectively,the first and second transfer rates Ra and Rb being lower than thepredetermined constant transfer rate Rp, wherein the predeterminedconstant transfer rate Rp, the first transfer rate Ra for the firstinformation signal, the second transfer rate Rb for the secondinformation signal, the size Ya of the first information signal, thesize Yb of the second information signal, a seek time Tab taken by thehead to move from the first area to the second area of the recordingmedium, and a seek time Tba taken by the head to move from the secondarea to the first area of the recording medium are in a relation asfollows:

(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)

[0028] A fourteenth aspect of this invention provides an apparatus forreproducing information from a recording medium having “n” areas onwhich “n” information signals are recorded respectively, where “n”denotes a predetermined natural number equal to or greater than 2. Theapparatus comprises a head for reproducing the “n” information signalsfrom the “n” areas of the recording medium and transmitting thereproduced “n” information signals on a time sharing basis and at apredetermined constant transfer rate Rp while moving among the “n” areasof the recording medium; and a buffer memory for receiving the “n”information signals from the head at the predetermined constant transferrate Rp, for temporarily storing the “n” information signals, and foroutputting the “n” information signals at transfer rates R1, R2, . . . ,Rn respectively, the transfer rates R1, R2, . . . , Rn being lower thanthe predetermined constant transfer rate Rp; wherein the predeterminedconstant transfer rate Rp, a sum ΣRn of the transfer rates R1, R2, . . ., Rn, a sum ΣYn of sizes of the “n” information signals, and a sum ΣSnof seek times taken by the head to move from present ones to next onesof the “n” areas of the recording medium are in a relation as follows:

ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0029] A fifteenth aspect of this invention provides an apparatus forrecording information on a recording medium having “n” areas, where “n”denotes a predetermined natural number equal to or greater than 2. Theapparatus comprises a buffer memory for receiving “n” informationsignals at transfer rates R1, R2, . . . , Rn respectively, fortemporarily storing the “n” information signals, and for outputting the“n” information signals at a predetermined constant transfer rate Rphigher than the transfer rates R1, R2, . . . , Rn; and a head forreceiving the “n” information signals from the buffer memory, and forrecording the “n” information signals on the “n” areas of the recordingmedium respectively on a time sharing basis and at the predeterminedconstant transfer rate Rp while moving among the “n” areas of therecording medium; wherein the predetermined constant transfer rate Rp, asum ΣRn of the transfer rates R1, R2, . . . , Rn, a sum ΣYn of sizes ofthe “n” information signals, and a sum ΣSn of seek times taken by thehead to move from present ones to next ones of the “n” areas of therecording medium are in a relation as follows:

ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0030] A sixteenth aspect of this invention provides an apparatus forrecording and reproducing information on and from a recording mediumhaving “n” areas, where “n” denotes a predetermined natural number equalto or greater than 2, wherein at least a first area among the “n” areasis loaded with a first information signal among “n” information signals.The apparatus comprises a head for reproducing the first informationsignal from the first area of the recording medium and transmitting thereproduced first information signal at a predetermined constant transferrate Rp; and a buffer memory for receiving the first information signalfrom the head at the predetermined constant transfer rate Rp, fortemporarily storing the first information signal, and for outputting thefirst information signal at a first transfer rate RI lower than thepredetermined constant transfer rate Rp; the buffer memory being forreceiving the “n” information signals except the first informationsignal at transfer rates R2, R3, . . . , Rn respectively, fortemporarily storing the “n” information signals except the firstinformation signal, and for outputting the “n” information signalsexcept the first information signal at the predetermined constanttransfer rate Rp, the transfer rates R2, R3, . . . , Rn being lower thanthe predetermined constant transfer rate Rp; the head being forreceiving the “n” information signals except the first informationsignal from the buffer memory, and for recording the “n” informationsignals except the first information signal on the “n” areas of therecording medium except the first area at the predetermined constanttransfer rate Rp; wherein the head implements reproduction of the firstinformation signal from the first area of the recording medium andrecording of the “n” information signals except the first informationsignal on the “n” areas of the recording medium except the first area ona time sharing basis while moving among the “n” areas of the recordingmedium; and wherein the predetermined constant transfer rate Rp, a sumΣRn of the transfer rates R1, R2, . . . , Rn, a sum ΣYn of sizes of the“n” information signals, and a sum Σn of seek times taken by the head tomove from present ones to next ones of the “n” areas of the recordingmedium are in a relation as follows:

ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0031] A seventeenth aspect of this invention provides an apparatus forreproducing information from a recording medium having “n” areas onwhich “n” information signals are recorded respectively, where “n”denotes a predetermined natural number equal to or greater than 2. Theapparatus comprises a head for reproducing the “n” information signalsfrom the “n” areas of the recording medium and transmitting thereproduced “n” information signals on a time sharing basis and at apredetermined constant transfer rate Rp while moving among the “n” areasof the recording medium; and a buffer memory for receiving the “n”information signals from the head at the predetermined constant transferrate Rp, for temporarily storing the “n” information signals, and foroutputting the “n” information signals at transfer rates R1, R2, . . . ,Rn respectively, the transfer rates R1, R2, . . . , Rn being lower thanthe predetermined constant transfer rate Rp; wherein the predeterminedconstant transfer rate Rp, a sum ΣRn of the transfer rates R1, R2, . . ., Rn, a sum ΣYn of sizes of the “n” information signals, and anallowable seek time S taken by the head to move from present one to nextone of the “n” areas of the recording medium are in a relation asfollows:

ΣYn≧Rp·ΣRn·n·S/(Rp−ΣRn)

[0032] An eighteenth aspect of this invention provides an apparatus forrecording information on a recording medium having “n” areas, where “n”denotes a predetermined natural number equal to or greater than 2. Theapparatus comprises a buffer memory for receiving “n” informationsignals at transfer rates R1, R2, . . . , Rn respectively, fortemporarily storing the “n” information signals, and for outputting the“n” information signals at a predetermined constant transfer rate Rphigher than the transfer rates R1, R2, . . . , Rn; and a head forreceiving the “n” information signals from the buffer memory, and forrecording the “n” information signals on the “n” areas of the recordingmedium respectively on a time sharing basis and at the predeterminedconstant transfer rate Rp while moving among the “n” areas of therecording medium; wherein the predetermined constant transfer rate Rp, asum ΣRn of the transfer rates R1, R2, . . . , Rn, a sum ΣYn of sizes ofthe “n” information signals, and an allowable seek time S taken by thehead to move from present one to next one of the “n” areas of therecording medium are in a relation as follows:

ΣYn≧Rp·ΣRn·n·S/(Rp−ΣRn)

[0033] A nineteenth aspect of this invention provides an apparatus forrecording and reproducing information on and from a recording mediumhaving “n” areas, where “n” denotes a predetermined natural number equalto or greater than 2, wherein at least a first area among the “n” areasis loaded with a first information signal among “n” information signals.The apparatus comprises a head for reproducing the first informationsignal from the first area of the recording medium and transmitting thereproduced first information signal at a predetermined constant transferrate Rp; and a buffer memory for receiving the first information signalfrom the head at the predetermined constant transfer rate Rp, fortemporarily storing the first information signal, and for outputting thefirst information signal at a first transfer rate R1 lower than thepredetermined constant transfer rate Rp; the buffer memory being forreceiving the “n” information signals except the first informationsignal at transfer rates R2, R3, . . . , Rn respectively, fortemporarily storing the “n” information signals except the firstinformation signal, and for outputting the “n” information signalsexcept the first information signal at the predetermined constanttransfer rate Rp, the transfer rates R2, R3, . . . , Rn being lower thanthe predetermined constant transfer rate Rp; the head being forreceiving the “n” information signals except the first informationsignal from the buffer memory, and for recording the “n” informationsignals except the first information signal on the “n” areas of therecording medium except the first area at the predetermined constanttransfer rate Rp; wherein the head implements reproduction of the firstinformation signal from the first area of the recording medium andrecording of the “n” information signals except the first informationsignal on the “n” areas of the recording medium except the first area ona time sharing basis while moving among the “n” areas of the recordingmedium; and wherein the predetermined constant transfer rate Rp, a sumΣRn of the transfer rates R1, R2, . . . , Rn, a sum ΣYn of sizes of the“n” information signals, and an allowable seek time S taken by the headto move from present one to next one of the “n” areas of the recordingmedium are in a relation as follows:

ΣYn≧Rp·ΣRn·n·S/(Rp−ΣRn)

[0034] A twentieth aspect of this invention provides an apparatus forreproducing information from a recording medium having “n” areas onwhich “n” information signals are recorded respectively, where “n”denotes a predetermined natural number equal to or greater than 2. Theapparatus comprises a head for reproducing the “n” information signalsfrom the “n” areas of the recording medium and transmitting thereproduced “n” information signals on a time sharing basis and at apredetermined constant transfer rate Rp while moving among the “n” areasof the recording medium; and a buffer memory for receiving the “n”information signals from the head at the predetermined constant transferrate Rp, for temporarily storing the “n” information signals, and foroutputting the “n” information signals at transfer rates R1, R2, . . . ,Rn respectively, the transfer rates R1, R2, . . . , Rn being lower thanthe predetermined constant transfer rate Rp, the buffer memory having acapacity Ym; wherein the predetermined constant transfer rate Rp, a sumΣRn of the transfer rates R1, R2, . . . , Rn, the capacity Ym of thebuffer memory, and a sum ΣSn of seek times taken by the head to movefrom present ones to next ones of the “n” areas of the recording mediumare in a relation as follows:

Ym≧Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0035] A twenty-first aspect of this invention provides an apparatus forrecording information on a recording medium having “n” areas, where “n”denotes a predetermined natural number equal to or greater than 2. Theapparatus comprises a buffer memory for receiving “n” informationsignals at transfer rates R1, R2, . . . , Rn respectively, fortemporarily storing the “n” information signals, and for outputting the“n” information signals at a predetermined constant transfer rate Rphigher than the transfer rates R1, R2, . . . , Rn, the buffer memoryhaving a capacity Ym; and a head for receiving the “n” informationsignals from the buffer memory, and for recording the “n” informationsignals on the “n” areas of the recording medium respectively on a timesharing basis and at the predetermined constant transfer rate Rp whilemoving among the “n” areas of the recording medium; wherein thepredetermined constant transfer rate Rp, a sum ΣRn of the transfer ratesR1, R2, . . . , Rn, the capacity Ym of the buffer memory, and a sum ΣSnof seek times taken by the head to move from present ones to next onesof the “n” areas of the recording medium are in a relation as follows:

Ym>Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0036] A twenty-second aspect of this invention provides an apparatusfor recording and reproducing information on and from a recording mediumhaving “n” areas, where “n” denotes a predetermined natural number equalto or greater than 2, wherein at least a first area among the “n” areasis loaded with a first information signal among “n” information signals.The apparatus comprises a head for reproducing the first informationsignal from the first area of the recording medium and transmitting thereproduced first information signal at a predetermined constant transferrate Rp; and a buffer memory for receiving the first information signalfrom the head at the predetermined constant transfer rate Rp, fortemporarily storing the first information signal, and for outputting thefirst information signal at a first transfer rate R1 lower than thepredetermined constant transfer rate Rp, the buffer memory having acapacity Ym; the buffer memory being for receiving the “n” informationsignals except the first information signal at transfer rates R2, R3, .. . , Rn respectively, for temporarily storing the “n” informationsignals except the first information signal, and for outputting the “n”information signals except the first information signal at thepredetermined constant transfer rate Rp, the transfer rates R2, R3, . .. , Rn being lower than the predetermined constant transfer rate Rp; thehead being for receiving the “n” information signals except the firstinformation signal from the buffer memory, and for recording the “n”information signals except the first information signal on the “n” areasof the recording medium except the first area at the predeterminedconstant transfer rate Rp; wherein the head implements reproduction ofthe first information signal from the first area of the recording mediumand recording of the “n” information signals except the firstinformation signal on the “n” areas of the recording medium except thefirst area on a time sharing basis while moving among the “n” areas ofthe recording medium; and wherein the predetermined constant transferrate Rp, a sum ΣRn of the transfer rates R1, R2, . . . , Rn, thecapacity Ym of the buffer memory, and a sum ΣSn of seek times taken bythe head to move from present ones to next ones of the “n” areas of therecording medium are in a relation as follows:

Ym>Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0037] A twenty-third aspect of this invention provides an apparatus forrecording information on a recording medium having “n” areas, where “n”denotes a predetermined natural number equal to or greater than 2. Theapparatus comprises a buffer memory for receiving “n” informationsignals at transfer rates R1, R2, . . . , Rn respectively, fortemporarily storing the “n” information signals, and for outputting the“n” information signals at a predetermined constant transfer rate Rphigher than the transfer rates R1, R2, . . . , Rn; a head for receivingthe “n” information signals from the buffer memory, and for recordingthe “n” information signals on the “n” areas of the recording mediumrespectively on a time sharing basis and at the predetermined constanttransfer rate Rp while moving among the “n” areas of the recordingmedium; means for deciding whether 6 r not parameters including thepredetermined constant transfer rate Rp, a sum ΣRn of the transfer ratesR1, R2, . . . , Rn, a sum ΣYn of sizes of the “n” information signals,and a sum ΣSn of seek times taken by the head to move from present onesto next ones of the “n” areas of the recording medium are in a relationas follows:

ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0038] means for, in cases where it is decided that the parameters arein the relation, permitting the head to record the “n” informationsignals on the “n” areas of the recording medium respectively; meansfor, in cases where it is decided that the parameters are not in therelation, selecting “p” information signals from among the “n”information signals, where “p” denotes a predetermined natural numbersmaller than “n”; means for deciding whether or not the parameters arein the relation regarding the “p” information signals; and means for, incases where it is decided that the parameters are in the relationregarding the “p” information signals, permitting the head to record the“p” information signals on “p” areas of the recording mediumrespectively, the “p” areas being among the “n” areas of the recordingmedium.

[0039] A twenty-fourth aspect of this invention provides an apparatusfor recording information on a recording medium having “n” areas, where“n” denotes a predetermined natural number equal to or greater than 2.The apparatus comprises a buffer memory for receiving “n” informationsignals at transfer rates R1, R2, . . . , Rn respectively, fortemporarily storing the “n” information signals, and for outputting the“n” information signals at a predetermined constant transfer rate Rphigher than the transfer rates R1, R2, . . . , Rn; a head for receivingthe “n” information signals from the buffer memory, and for recordingthe “n” information signals on the “n” areas of the recording mediumrespectively on a time sharing basis and at the predetermined constanttransfer rate Rp while moving among the “n” areas of the recordingmedium; means for deciding whether or not parameters including thepredetermined constant transfer rate Rp, a sum ΣRn of the transfer ratesR1, R2, . . . , Rn, a sum ΣYn of sizes of the “n” information signals,and a sum ΣSn of seek times taken by the head to move from present onesto next ones of the “n” areas of the recording medium are in a relationas follows:

ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0040] means for, in cases where it is decided that the parameters arein the relation, permitting the head to record the “n” informationsignals on the “n” areas of the recording medium respectively; and meansfor, in cases where it is decided that the parameters are not in therelation, controlling the head to record the “n” information signals ona common area in the recording medium on a time sharing basis.

[0041] A twenty-fifth aspect of this invention is based on thetwenty-fourth aspect thereof, and provides an apparatus furthercomprising means for rearranging the “n” information signals into “n”rearrangement-resultant information signals in the buffer memory, andfor sequentially transmitting the “n” rearrangement-resultantinformation signals from the buffer memory to the head to sequentiallyrecord the “n” rearrangement-resultant signals.

[0042] A twenty-sixth aspect of this invention provides an apparatus forrecording information on a recording medium. The apparatus comprises abuffer memory for receiving “n” information signals at transfer ratesR1, R2, . . . , Rn respectively, for temporarily storing the “n”information signals, and for outputting the “n” information signals at apredetermined constant transfer rate Rp higher than the transfer ratesR1, R2, . . . , Rn, where “n” denotes a predetermined natural numberequal to or greater than 2; a head for receiving the “n” informationsignals from the buffer memory, and for recording the “n” informationsignals on the recording medium on a time sharing basis and at thepredetermined constant transfer rate Rp; first means for causing thehead to record the “n” information signals on at least two areas in therecording medium on a time sharing basis while moving the head among theareas in the recording medium under conditions where the predeterminedconstant transfer rate Rp, a sum ΣRn of the transfer rates R1, R2, . . ., Rn, a sum ΣYn of sizes of the “n” information signals, and a sum ΣSnof seek times taken by the head to move from present ones to next onesof the areas in the recording medium are in a relation as follows:

ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0043] second means for causing the head to record the “n” informationsignal on a common area in the recording medium on a time sharing basis;and third means for selecting and enabling one of the first and secondmeans.

[0044] A twenty-seventh aspect of this invention is based on thetwenty-sixth aspect thereof, and provides an apparatus wherein the thirdmeans comprises means for selecting and enabling one of the first andsecond means in response to one of types of the “n” information signals,user's requirement, apparatus specifications, a type of the recordingmedium, and a condition of a usable area in the recording medium.

[0045] A twenty-eighth aspect of this invention is based on thefourteenth aspect thereof, and provides an apparatus further comprisingmeans for partitioning the buffer memory into “n” areas in accordancewith values of the transfer rates R1, R2, . . . , Rn, wherein the “n”areas in the buffer memory are assigned to the “n” information signalsrespectively.

[0046] A twenty-ninth aspect of this invention is based on thefourteenth aspect thereof, and provides an apparatus further comprisingmeans for partitioning the buffer memory into “n” areas in accordancewith an operation mode, wherein the “n” areas in the buffer memory areassigned to the “n” information signals respectively.

[0047] A thirtieth aspect of this invention provides aninformation-signal communication apparatus comprising the apparatus ofthe fourteenth aspect of this invention and an interface connected withthe buffer memory for communication with an external.

[0048] A thirty-first aspect of this invention provides aninformation-signal recording medium having “n” areas on which “n”information signals are recorded respectively, where “n” denotes apredetermined natural number equal to or greater than 2, wherein the “n”information signals can be reproduced from the “n” areas and can betransmitted by a head on a time sharing basis and at a predeterminedconstant transfer rate Rp while the head moves among the “n” areas ofthe recording medium, wherein the “n” information signals outputted fromthe head can be received by a buffer memory at the predeterminedconstant transfer rate Rp and can be temporarily stored in the buffermemory before being outputted from the buffer memory at transfer ratesR1, R2, . . . , Rn respectively, the transfer rates R1, R2, . . . , Rnbeing lower than the predetermined constant transfer rate Rp, whereinthe predetermined constant transfer rate Rp, a sum ΣRn of the transferrates R1, R2, . . . , Rn, a sum ΣYn of sizes of the “n” informationsignals, and a sum ΣSn of seek times taken by the head to move frompresent ones to next ones of the “n” areas of the recording medium arein a relation as follows:

ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)

[0049] A thirty-second aspect of this invention provides an apparatusfor recording and reproducing information on and from a recording mediumhaving first and second areas and a management area, the management areastoring management information representing addresses in the first andsecond areas. The apparatus comprises a first buffer memory forreceiving a first information signal at a first transfer rate, fortemporarily storing the first information signal, and for outputting thefirst information signal at a predetermined constant transfer ratehigher than the first transfer rate; a second buffer memory forreceiving a second information signal at a second transfer rate lowerthan the predetermined constant transfer rate, for temporarily storingthe second information signal, and for outputting the second informationsignal at the predetermined constant transfer rate; a head for receivingthe first and second information signals from the first and secondbuffer memories and recording the first and second information signalson the first and second areas of the recording medium respectively on atime sharing basis and at the predetermined constant transfer rate whilemoving between the first and second areas of the recording medium; meansfor controlling the head to reproduce the management information fromthe management area of the recording medium before the head records thefirst and second information signals; means for deriving the addressesfrom the reproduced management information; means for searching forunoccupied regions in the first and second areas of the recording mediumin response to the derived addresses; and means for deciding whether ornot the first and second information signals can be recorded on theunoccupied regions while recording continuities related to the first andsecond information signals are maintained.

[0050] A thirty-third aspect of this invention is based on thethirty-second aspect thereof, and provides an apparatus wherein thedeciding means comprises means for deciding whether or not the first andsecond information signals can be recorded on the unoccupied regionswhile the predetermined constant transfer rate Rp, the first transferrate Ra for the first information signal, the second transfer rate Rbfor the second information signal, a size Ya of the first informationsignal, a size Yb of the second information signal, a seek time Tabtaken by the head to move from the first area to the second area of therecording medium, and a seek time Tba taken by the head to move from thesecond area to the first area of the recording medium are in a relationas follows:

(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)

[0051] A thirty-fourth aspect of this invention is based on thethirty-second aspect thereof, and provides an apparatus wherein thedeciding means comprises means for deciding whether or not the first andsecond information signals can be recorded on the unoccupied regionswhile the predetermined constant transfer rate Rp, the first transferrate Ra for the first information signal, the second transfer rate Rbfor the second information signal, a size Ya of the first informationsignal, a size Yb of the second information signal, and a maximumallowable seek time Tmax taken by the head to move on the recordingmedium are in a relation as follows:

(Ya+Yb)≧2·Rp·(Ra+Rb)·Tmax/(Rp−Ra−Rb)

[0052] A thirty-fifth aspect of this invention provides an apparatus forrecording and reproducing information on and from a recording mediumhaving first and second areas and a management area, the first areabeing loaded with a first information signal, the management areastoring management information representing addresses in the first andsecond areas. The apparatus comprises a head for reproducing the firstinformation signal from the first area of the recording medium andtransmitting the reproduced first information signal at a predeterminedconstant transfer rate; a first buffer memory for receiving the firstinformation signal from the head at the predetermined constant transferrate Rp, for temporarily storing the first information signal, and foroutputting the first information signal at a first transfer rate lowerthan the predetermined constant transfer rate; a second buffer memoryfor receiving a second information signal at a second transfer ratelower than the predetermined constant transfer rate, for temporarilystoring the second information signal, and for outputting the secondinformation signal at the predetermined constant transfer rate; the headbeing for receiving the second information signal from the second buffermemory, and for recording the second information signal on the secondarea of the recording medium at the predetermined constant transferrate; wherein the head implements reproduction of the first informationsignal from the first area of the recording medium and recording of thesecond information signal on the second area of the recording medium ona time sharing basis while moving between the first and second areas ofthe recording medium; means for controlling the head to reproduce themanagement information from the management area of the recording mediumbefore the head records the second information signal; means forderiving the addresses from the reproduced management information; meansfor searching for an unoccupied region in the second area of therecording medium in response to the derived addresses; and means fordeciding whether or not the second information signal can be recorded onthe unoccupied region while a recording continuity related to the secondinformation signal is maintained.

[0053] A thirty-sixth aspect of this invention is based on thethirty-fifth aspect thereof, and provides an apparatus wherein thedeciding means comprises means for deciding whether or not the secondinformation signal can be recorded on the unoccupied region while thepredetermined constant transfer rate Rp, the first transfer rate Ra forthe first information signal, the second transfer rate Rb for the secondinformation signal, a size Ya of the first information signal, a size Ybof the second information signal, a seek time Tab taken by the head tomove from the first area to the second area of the recording medium, anda seek time Tba taken by the head to move from the second area to thefirst area of the recording medium are in a relation as follows:

(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)

[0054] A thirty-seventh aspect of this invention is based on thethirty-fifth aspect thereof, and provides an apparatus wherein thedeciding means comprises means for deciding whether or not the secondinformation signal can be recorded on the unoccupied region while thepredetermined constant transfer rate Rp, the first transfer rate Ra forthe first information signal, the second transfer rate Rb for the secondinformation signal, a size Ya of the first information signal, a size Ybof the second information signal, and a maximum allowable seek time Tmaxtaken by the head to move on the recording medium are in a relation asfollows:

(Ya+Yb)≧2·Rp·(Ra+Rb)·Tmax/(Rp−Ra−Rb)

[0055] A thirty-eighth aspect of this invention is based on thethirty-second aspect thereof, and provides an apparatus furthercomprising means for indicating a result of the deciding by the decidingmeans.

[0056] A thirty-ninth aspect of this invention is based on thethirty-second aspect thereof, and provides an apparatus furthercomprising means for calculating a first total capacity of theunoccupied regions, means for calculating a second total capacity ofusable portions of the unoccupied regions, means for calculating anrecording efficiency equal to a ratio between the first total capacityand the second total capacity, and means for indicating the calculatedrecording efficiency.

[0057] According to the basic aspects of this invention, the signaltransfer rate related to the recording and reproduction of informationon and from a recording medium is preferably fixed to the predeterminedconstant transfer rate Rp.

[0058] Generally, this invention can operate on a recording medium suchas a DVD-ROM, a DVD-RW, a DVD-RAM, a DVD+RW, and an HDD magnetic disc.

[0059] A DVD-ROM or a DVD-RW is subjected to CLV (constant linearvelocity) control by a disc drive. Thus, the signal transfer rate isfixed throughout the whole area of the DVD-ROM or the DVD-RW.

[0060] A DVD-RAM is divided into zones. The DVD-RAM is subjected to zoneCLV by a disc drive. The signal transfer rate varies from zone to zoneby only several percent. This invention is adaptable to such aslightly-varying signal transfer rate.

[0061] Regarding a DVD+RW or an HDD magnetic disc, the signal transferrate sometimes depends on a disc radial position. This invention can beapplied to a disc area in which the signal transfer rate varies byseveral percent to several tens of percent.

[0062] In these case, it is preferable to calculate the signal transferrate (Rp) regarding a recording medium as a minimum signal transfer ratewhich occurs when recording or reproduction is performed.

[0063] In this invention, information is recorded on and reproduced fromtwo or more areas of a recording medium. The two or more areas of therecording medium may be a common area. In this case, this invention isdesigned to operate in one of the following modes. During a first modeof operation, first data are reproduced from an area of a recordingmedium and a portion of the reproduced first data is changed to formsecond data, and the second data are recorded on the same area of therecording medium. During a second mode of operation, data are recordedon an area of a recording medium, and then the data are reproducedtherefrom and the reproduced data are analyzed to verify whether thedata have been correctly recorded on the area of the recording medium.

BRIEF DESCRIPTION OF THE DRAWINGS

[0064]FIG. 1 is a block diagram of an information-signal recording andreproducing apparatus according to a first embodiment of this invention.

[0065]FIG. 2 is a diagram of a portion of the apparatus in FIG. 1.

[0066]FIG. 3 is a diagram of a portion of the apparatus in FIG. 1 whichis operating in a two-signal playback mode.

[0067]FIG. 4 is a diagram of first areas in an optical disc.

[0068]FIG. 5 is a diagram of second areas in the optical disc.

[0069]FIG. 6 is a flowchart of a segment of a program for a systemcontroller in FIG. 1 which relates to the two-signal playback mode ofoperation.

[0070]FIG. 7 is a time-domain diagram of the degrees of occupancy offirst and second areas in a track buffer memory in FIG. 1 which occur inthe two-signal playback mode of operation.

[0071]FIG. 8 is a diagram of a portion of the apparatus in FIG. 1 whichis operating in a two-signal recording mode.

[0072]FIG. 9 is a flowchart of a segment of the program for the systemcontroller in FIG. 1 which relates to the two-signal recording mode ofoperation.

[0073]FIG. 10 is a time-domain diagram of the degrees of occupancy ofthe first and second areas in the track buffer memory in FIG. 1 whichoccur in the two-signal recording mode of operation.

[0074]FIG. 11 is a diagram of a portion of the apparatus in FIG. 1 whichis operating in a signal recording/playback mode.

[0075]FIG. 12 is a flowchart of a segment of the program for the systemcontroller in FIG. 1 which relates to the signal recording/playback modeof operation.

[0076]FIG. 13 is a time-domain diagram of the degrees of occupancy ofthe first and second areas in the track buffer memory in FIG. 1 whichoccur in the signal recording/playback mode of operation.

[0077]FIG. 14 is a block diagram of an information-signal recording andreproducing apparatus according to a second embodiment of thisinvention.

[0078]FIG. 15 is a block diagram of an information-signal communicationapparatus according to a third embodiment of this invention.

[0079]FIG. 16 is a block diagram of an information-signal communicationapparatus according to a fourth embodiment of this invention.

[0080]FIG. 17 is a block diagram of an information-signal recording andreproducing apparatus according to a fifth embodiment of this invention.

[0081]FIG. 18 is a diagram of a portion of the apparatus in FIG. 17.

[0082]FIG. 19 is a diagram of sub-areas in a first area of an opticaldisc.

[0083]FIG. 20 is a diagram of sub-areas in a second area of the opticaldisc.

[0084]FIG. 21 is a diagram of sub-areas in an n-th area of the opticaldisc.

[0085]FIG. 22 is a diagram of sub-areas in a management area of theoptical disc.

[0086]FIG. 23 is a time-domain diagram of the degrees of occupancy ofareas in a track buffer memory in FIG. 17 which occur in amultiple-signal playback mode of operation.

[0087]FIG. 24 is a time-domain diagram of the degrees of occupancy ofthe areas in the track buffer memory in FIG. 17 which occur in amultiple-signal recording mode of operation.

[0088]FIG. 25 is a block diagram of an information-signal communicationapparatus according to a sixth embodiment of this invention.

[0089]FIG. 26 is a time-domain diagram of conditions of informationsignals which occur during a first recording procedure in a seventhembodiment of this invention.

[0090]FIG. 27 is a time-domain diagram of conditions of informationsignals which occur during a second recording procedure in the seventhembodiment of this invention.

[0091]FIG. 28 is a time-domain diagram of conditions of informationsignals which occur during a third recording procedure in the seventhembodiment of this invention.

[0092]FIG. 29 is a time-domain diagram of conditions of informationsignals which occur during a fourth recording procedure in the seventhembodiment of this invention.

[0093]FIG. 30 is a block diagram of an information-signal recording andreproducing apparatus according to an eighth embodiment of thisinvention.

[0094]FIG. 31 is a diagram of a portion of the apparatus in FIG. 30.

[0095]FIG. 32 is a diagram of sub-areas in a management area of anoptical disc in FIG. 31.

[0096]FIG. 33 is a diagram of a first example of indication on a displayin FIG. 30.

[0097]FIG. 34 is a diagram of a second example of indication on thedisplay in FIG. 30.

[0098]FIG. 35 is a diagram of a third example of indication on thedisplay in FIG. 30.

[0099]FIG. 36 is a flowchart of a segment of a program for a systemcontroller in FIG. 30 which relates to a two-signal recording mode ofoperation.

[0100]FIG. 37 is a flowchart of a segment of the program for the systemcontroller in FIG. 30 which relates to a signal recording/playback modeof operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

[0101]FIG. 1 shows an information-signal recording and reproducingapparatus 10A according to a first embodiment of this invention. Theapparatus 10A operates on an information-signal recording mediumincluding an optical disc. Examples of the optical disc are a DVD-ROM, aDVD-RAM, a DVD-RW, and a DVD+RW. Alternatively, the informationrecording medium may include a magnetic disc such as a hard disc or afloppy disc. The information recording medium may include asemiconductor memory.

[0102] As shown in FIG. 1, the apparatus 10A includes a spindle motor11, and a turntable 12 connected to the shaft of the spindle motor 11.An optical disc (an information-signal recording medium) 13 can beplaced on the turntable 12. The apparatus 10A further includes anoptical head (an optical pickup) 14, a driver 15, an amplifier unit 16,a servo unit 17, a signal processor 18, a track buffer memory 19, anaudio-video encoding and decoding unit 20, a memory 21, a systemcontroller 22, a key input unit 23, and an input/output terminal 24.

[0103] When the optical disc 13 is placed on the turntable 12, thespindle motor 11 rotates the turntable 12 and the optical disc 13. Inthe case where the optical disc 13 is of a rewritable type, the opticalhead 14 writes and reads information thereon and therefrom. In the casewhere the optical disc 13 is designed exclusively for playback, theoptical head 14 only reads information therefrom. The spindle motor 11is connected to the driver 15 and the servo unit 17. The optical head 14is connected to the amplifier unit 16 and the driver 15. The amplifierunit 16 is connected to the servo unit 17 and the signal processor 18.The driver 15 is connected to the servo unit 17. The signal processor 18is connected to the track buffer memory 19 and the audio-video encodingand decoding unit 20. The audio-video encoding and decoding unit 20 isconnected to the memory 21 and the input/output terminal 24. The systemcontroller 22 is connected to the amplifier unit 16, the servo unit 17,the signal processor 18, the audio-video encoding and decoding unit 20,and the key input unit 23.

[0104] The spindle motor 11 is driven and controlled by the driver 15.The spindle motor 11 rotates the turntable 12 and the optical disc 13.The spindle motor 11 is provided with an FG generator and a rotationalposition sensor (an angular position sensor). The rotational positionsensor includes, for example, a Hall element. The FG generator outputsan FG signal (a rotational speed signal). The Hall element outputs arotational position signal. The FG signal and the rotational positionsignal are fed back to the driver 15 and the servo unit 17 as rotationservo signals.

[0105] The optical head 14 faces the optical disc 13 placed on theturntable 12. A feed motor (not shown) moves the optical head 14radially with respect to the optical disc 13. The feed motor is drivenby the driver 15. The optical head 14 includes a semiconductor laser, acollimator lens, and an objective lens. The semiconductor laser acts asa source for emitting a light beam (a laser beam). The emitted laserbeam is focused into a laser spot on the optical disc 13 by thecollimator lens and the objective lens. The optical head 14 includes a2-axis actuator for driving the objective lens to implement focusing andtracking of the laser spot with respect to the optical disc 13. Thesemiconductor laser is driven by a laser drive circuit in the opticalhead 14. In the case where an information signal such as an audio signalor an audio-video signal is recorded, the information signal issubjected to waveform correction by a waveform correction circuit in theamplifier unit 16 before being fed to the laser drive circuit. The2-axis actuator is driven by the driver 15.

[0106] The key input unit 23 includes a plurality of keys which can beoperated by a user. The key input unit 23 generates command signals inaccordance with its operation by the user. The command signals aretransmitted from the key input unit 23 to the system controller 22. Thecommand signals include a command signal for starting a recording modeof operation of the apparatus 10A, and a command signal for starting aplayback mode of operation of the apparatus 10A. The key input unit 23generates control data in accordance with its operation by the user. Thecontrol data are transmitted from the key input unit 23 to the systemcontroller 22.

[0107] The system controller 22 includes, for example, a microcomputeror a similar device which operates in accordance with a program storedin its internal ROM. The system controller 22 controls the amplifierunit 16, the servo unit 17, the signal processor 18, and the audio-videoencoding and decoding unit 20 in response to the command signals fedfrom the key input unit 23.

[0108] Control data can be fed to the system controller 22 via an inputterminal (not shown). The control data fed to the system controller 22via the input terminal, and the control data fed to the systemcontroller 22 from the key input unit 23 include a signal for adjustingthe resolution of pictures represented by contents information to berecorded, a signal for separating quickly-moving scenes such as carracing scenes represented by contents information, and a signal forgiving priority to a recording time. The system controller 22 changes anactual recording time in accordance with the control data. The systemcontroller 22 enables the setting of the actual recording time to beselected by the user.

[0109] When the apparatus 10A is required to start to operate in theplayback mode, the key input unit 23 is actuated to generate theplayback start command signal. The playback start command signal istransmitted from the key input unit 23 to the system controller 22. Thesystem controller 22 controls the amplifier unit 16 and the servo unit17 in response to the playback start command signal, thereby startingthe playback mode of operation of the apparatus 10A. The control of theservo unit 17 includes steps of controlling the driver 15. Firstly, thesystem controller 22 starts rotation of the optical disc 13 andapplication of a laser spot thereon through the control of the driver15. The optical head 14 is controlled by the driver 15, thereby readingout address information from the optical disc 13. For example, theaddress information is contained in management information stored in amanagement area of the optical disc 13. The read-out address informationis transmitted from the optical head 14 to the system controller 22 viathe amplifier unit 16. The system controller 22 finds or decides atarget sector (a target track portion) to be played back by referring tothe address information. The system controller 22 controls the opticalhead 14 via the servo unit 17, the driver 15, and the feed motor,thereby moving the optical head 14 radially with respect to the opticaldisc 13 and hence moving the laser spot to the target sector on theoptical disc 13. When the movement of the laser spot to the targetsector is completed, the system controller 22 operates to start thereproduction of a signal from the target sector on the optical disc 13.In this way, the playback mode of operation of the apparatus 10A isstarted. During the playback mode of operation of the apparatus 10A, thetarget sector is repetitively changed from one to another.

[0110] During the playback mode of operation of the apparatus 10A, theoptical head 14 scans the optical disc 13 and generates an RF signalcontaining information read out therefrom. A unit of generation of theRF signal corresponds to one correction block of the informationrecorded on the optical disc 13. The optical head 14 outputs the RFsignal to the amplifier unit 16. The amplifier unit 16 enlarges the RFsignal. In addition, the amplifier unit 16 generates a main reproducedsignal, and tracking and focusing servo signals (tracking error andfocusing error signals) from the enlarged RF signal. The amplifier unit16 includes an equalizer for optimizing the frequency aspect of the mainreproduced signal. Also, the amplifier unit 16 includes a PLL (phaselocked loop) circuit for extracting a bit clock signal from theequalized main reproduced signal, and for generating a speed servosignal from the equalized main reproduced signal. Furthermore, theamplifier unit 16 includes a jitter generator for comparing the timebases of the bit clock signal and the equalized main reproduced signal,and for detecting jitter components from the results of the time-basecomparison. A signal of the detected jitter components is transmittedfrom the amplifier unit 16 to the system controller 22. The tracking andfocusing servo signals and the speed servo signal are transmitted fromthe amplifier unit 16 to the servo unit 17. The equalized mainreproduced signal is transmitted from the amplifier unit 16 to thesignal processor 18.

[0111] The servo unit 17 receives the speed servo signal and thetracking and focusing servo signals from the amplifier unit 16. Theservo unit 17 receives the rotation servo signals from the spindle motor11. In response to these servo signals, the servo unit 17 implementscorresponding servo control processes.

[0112] Specifically, the servo unit 17 generates a rotation controlsignal on the basis of the speed servo signal and the rotation servosignals. The rotation control signal is transmitted from the servo unit17 to the spindle motor 11 via the driver 15. The spindle motor 11rotates at a speed depending on the rotation control signal. Therotation control signal is designed to rotate the optical disc 13 at agiven constant linear velocity.

[0113] In addition, the servo unit 17 generates servo control signals onthe basis of the focusing and tracking servo signals. The servo controlsignals are transmitted from the servo unit 17 to the 2-axis actuator inthe optical head 14 via the driver 15. The 2-axis actuator controls thelaser spot on the optical disc 13 in response to the servo controlsignals, and thereby implements focusing and tracking of the laser spotwith respect to the optical disc 13.

[0114] During the playback mode of operation of the apparatus 10A, thesignal processor 18 receives the main reproduced signal from theamplifier unit 16. The signal processor 18 is controlled by the systemcontroller 22, thereby converting the main reproduced signal into acorresponding reproduced digital signal. The signal processor 18 detectsa sync signal from the reproduced digital signal. The signal processor18 decodes an EFM+ signal (an 8-16 modulation signal) of the reproduceddigital signal into NRZ data, that is, non-return-to-zero data. Thesignal processor 18 subjects the NRZ data to an error correction processfor every correction block, thereby generating a sector address signaland first and second information signals. The sector address signalrepresents the address of a currently-accessed sector on the opticaldisc 13. The sync signal and the sector address signal are fed from thesignal processor 18 to the system controller 22. It should be noted thatthe first and second information signals generated by the signalprocessor 18 correspond to first and second information signalsresulting from compression at variable transfer rates (variabletransmission rates) during a recording mode of operation.

[0115] During the playback mode of operation of the apparatus 10A, thesignal processor 18 temporarily stores the first and second informationsignals in the track buffer memory 19. Thus, the signal processor 18writes the first and second information signals into the track buffermemory 19, and reads the first and second information signals therefrom.Writing and reading the first and second information signals into andfrom the track buffer memory 19 are controlled to absorb a time-domainchange in the transfer rates of the first and second informationsignals. The track buffer memory 19 includes, for example, a D-RAMhaving a capacity of 64 Mbytes. The signal processor 18 outputs theread-out signal (the first and second information signals read out fromthe track buffer memory 19) to the audio-video encoding and decodingunit 20.

[0116] In the case where the first and second information signals fedfrom the track buffer memory 19 via the signal processor 18 arecompressed MPEG2 data in which audio data and video data aremultiplexed, the audio-video encoding and decoding unit 20 separates thefirst and second information signals into compressed audio data andcompressed video data. The audio-video encoding and decoding unit 20expands and decodes the compressed audio data into non-compressed audiodata. In addition, the audio-vide encoding and decoding unit 20 expandsand decodes the compressed video data into non-compressed video data.During the expansively decoding process, the audio-video encoding anddecoding unit 20 temporarily stores signals and data in the memory 21.The memory 21 includes, for example, a D-RAM having a capacity of 64Mbytes. The audio-video encoding and decoding unit converts thenon-compressed audio data into a corresponding analog audio signalthrough digital-to-analog conversion. Also, the audio-video encoding anddecoding unit 20 converts the non-compressed video data into acorresponding analog video signal through digital-to-analog conversion.It should be noted that the conversion of the non-compressed audio andvideo data into the analog audio and video signals may be implemented bydigital-to-analog converters provided externally of the audio-videoencoding and decoding unit 20. The audio-video encoding and decodingunit applies the analog audio signal and the analog video signal to theinput/output terminal 24. The analog audio signal and the analog videosignal are transmitted to an external via the input/output terminal 24.

[0117] The data rate of the expansively decoding process by theaudio-video encoding and decoding unit 20, that is, the data transferrate (the data transmission rate) in the expansively decoding process,is equalized to an expansion data rate which is set in accordance withthe type of the related recording mode of operation of the apparatus10A. Specifically, the audio-video encoding and decoding unit 20 canimplement the expansively decoding process at a expansion data ratewhich can be changed among plural different expansion data rates. Theaudio-video encoding and decoding unit 20 selects one from among theplural different expansion data rates as a desired expansion data ratein accordance with the type of the related recording mode of operationof the apparatus 10A. The audio-video encoding and decoding unit 20executes the expansively encoding process at the desired expansion datarate. Information of the type of the recording mode of operation of theapparatus 10A is recorded on the optical disc 13 as control data whichmay be contained in the management information. During an initial stageof the playback of the optical disc 13, the control data are read outtherefrom before being transmitted to the system controller 22. Thesystem controller 22 sets the expansion data rate in the audio-videoencoding and decoding unit 20 in accordance with the control data.

[0118] When the apparatus 10A is required to start to operate in therecording mode, the key input unit 23 is actuated to generate therecording start command signal. The recording start command signal istransmitted from the key input unit 23 to the system controller 22. Thesystem controller 22 controls the amplifier unit 16 and the servo unit17 in response to the recording start command signal, thereby startingthe recording mode of operation of the apparatus 10A. The control of theservo unit 17 includes steps of controlling the driver 15. Firstly, thesystem controller 22 starts rotation of the optical disc 13 andapplication of a laser spot thereon through the control of the driver15. The optical head 14 is controlled by the driver 15, thereby readingout address information from the optical disc 13. For example, theaddress information is contained in the management information stored inthe management area of the optical disc 13. The read-out addressinformation is transmitted from the optical head 14 to the systemcontroller 22 via the amplifier unit 16. The system controller 22 findsor decides a target sector (a target track portion), on which a signalis to be recorded, by referring to the address information. The systemcontroller 22 controls the optical head 14 via the servo unit 17, thedriver 15, and the feed motor, thereby moving the optical head 14radially with respect to the optical disc 13 and hence moving the laserspot to the target sector on the optical disc 13. During the recordingmode of operation of the apparatus 10A, the target sector isrepetitively changed from one to another.

[0119] During the recording mode of operation of the apparatus 10A, anaudio signal and a video signal to be recorded are fed via theinput/output terminal 24 to the audio-video encoding and decoding unit20. The audio-video encoding and decoding unit 20 converts the audiosignal into corresponding audio data through analog-to-digitalconversion. In addition, the audio-video encoding and decoding unit 20converts the video signal into corresponding video data throughanalog-to-digital conversion. It should be noted that the conversion ofthe audio and video signals into the audio and video data may beimplemented by analog-to-digital converters provided externally of theaudio-video encoding and decoding unit 20. The audio-video encoding anddecoding unit 20 compressively encodes the audio data and the video datainto MPEG2 audio data and MPEG2 video data at a rate depending on thetype of the recording mode. The audio-video encoding and decoding unit20 multiplexes the MPEG2 audio data and the MPEG2 video data to formmultiplexed MPEG2 data. The audio-video encoding and decoding unit 20outputs the multiplexed MPEG2 data to the signal processor 18. The datarate of the compressively encoding process by the audio-video encodingand decoding unit 20, that is, the data transfer rate (the datatransmission rate) in the compressively encoding process, is equalizedto a compression data rate which is selected from among plural differentrates in accordance with the type of the recording mode of operation ofthe apparatus 10A. During the compressively encoding process, theaudio-video encoding and decoding unit 20 temporarily stores data in thememory 21.

[0120] It should be noted that the multiplexed MPEG2 data may bereplaced by still-picture data or computer data such as program filedata. In this case, the still-picture data or the computer data aretransmitted to the system controller 22 via an interface (not shown).The system controller 22 transfers the still-picture data or thecomputer data to the signal processor 18.

[0121] During the recording mode of operation of the apparatus 10A, thesignal processor 18 adds error correction code signals (ECC signals) tothe multiplexed MPEG2 data, the still-picture data, or the computerdata. The signal processor 18 subjects the ECC-added data to NRZ andEFM+ encoding processes. The signal processor 18 adds a sync signal tothe encoding-resultant data to form sync-added data. The sync signal isfed from the system controller 22. The sync-added data are temporarilystored in the track buffer memory 19. The sync-added data are read outfrom the track buffer memory 19 at a data rate corresponding to a datarate of signal recording on the optical disc 13. The signal processor 18subjects the read-out data to given modulation for record. The signalprocessor 18 outputs the modulation-resultant signal to the amplifierunit 16. The amplifier unit 16 corrects the waveform of the outputsignal of the signal processor 18. The amplifier unit 16 outputs thewaveform-correction-resultant signal to the laser drive circuit in theoptical head 14. The optical head 14 records the output signal of theamplifier unit 16 on the target sector (the target track portion) on theoptical disc 13.

[0122] The amplifier unit 16 informs the system controller 22 ofdetected jitter components. The system controller 22 subjects thedetected jitter components to analog-to-digital conversion to generate ameasured jitter value. During the recording mode of operation of theapparatus 10A, the system controller 22 adjusts the degree orcharacteristic of the waveform correction by the amplifier unit 16 inresponse to the measured jitter value and an asymmetry value.

[0123] Operation of the apparatus 10A can be changed among variousmodes. During a first mode of operation which corresponds to thepreviously-mentioned playback mode of operation, the apparatus 10Areproduces an audio signal (audio signals) or an audio-video signal(audio-video signals) from the optical disc 13. During a second mode ofoperation which corresponds to the previously-mentioned recording modeof operation, the apparatus 10A records an audio signal or anaudio-video signal on the optical disc 13. During a third mode ofoperation, the apparatus 10A records an audio signal or an audio-videosignal on one area of the optical disc 13 while reproducing an audiosignal or an audio-video signal from another area of the optical disc13. During a fourth mode of operation, the apparatus 10A reproduces anaudio signal or an audio-video signal from one area of the optical disc13 while recording an audio signal or an audio-video signal on anotherarea of the optical disc 13. During a fifth mode of operation, theapparatus 10A reproduces an audio signal or an audio-video signal fromone area of the optical disc 13 while reproducing an audio signal or anaudio-video signal from another area of the optical disc 13. During asixth mode of operation, the apparatus 10A records an audio signal or anaudio-video signal on one area of the optical disc 13 while recording anaudio signal or an audio-video signal on another area of the opticaldisc 13. These various modes of operation of the apparatus 10A meetuser's requests for the implementation of an after-recording process anda different-channel-program recording process.

[0124] The apparatus 10A can record first and second information signalson different areas of the optical disc 13, respectively, on a timesharing basis. The first and second information signals are first andsecond audio-video information signals respectively.

[0125] Alternatively, the first and second information signals may befirst and second audio information signals respectively. The apparatus10A can record only one of the first and second information signals onthe optical disc 13.

[0126] The apparatus 10A can reproduce first and second informationsignals from different areas of the optical disc 13, respectively, on atime sharing basis. The first and second information signals are firstand second audio-video information signals respectively. Alternatively,the first and second information signals may be first and second audioinformation signals respectively. The apparatus 10A can reproduce onlyone of the first and second information signals from the optical disc13.

[0127]FIG. 2 shows a portion of the apparatus 10A. The amplifier unit 16and the signal processor 18 are omitted from FIG. 2 for a betterunderstanding. As shown in FIG. 2, the optical disc 13 has first areas13 a assigned to a first information signal “A”, and second areas 13 bassigned to a second information signal “B”. The first areas 13 a haveequal sizes, and are separate from each other. The second areas 13 bhave equal sizes, and are separate from each other. The second areas 13b are separate from the first areas 13 a. The first information signal“A” is divided into blocks each having a predetermined size (apredetermined total number of bits) Ya. The predetermined size Ya is aunit (a unit capacity) for continuous reproduction (or continuousrecording) of information, or a unit (a unit capacity) for reproduction(or recording) of continuous information. The first areas 13 a areallocated to the blocks of the first information signal “A”,respectively. The second information signal “B” is divided into blockseach having a predetermined size (a predetermined total number of bits)Yb equal to or different from the predetermined size Ya. Thepredetermined size Yb is a unit (a unit capacity) for continuousreproduction (or continuous recording) of information, or a unit (a unitcapacity) for reproduction (or recording) of continuous information. Thesecond areas 13 b are allocated to the blocks of the second informationsignal “B”, respectively. The first information signal “A” and thesecond information signal “B” are related or unrelated to each other.Each of the first and second information signals “A” and “B” representsaudio data, video data, audio-video data, or computer data.

[0128] The track buffer memory 19 has a first area 19 a assigned to thefirst information signal “A”, and a second area 19 b assigned to thesecond information signal “B”.

[0129] With reference to FIG. 2, the optical head 14 transfers the firstinformation signal “A” and the second information signal “B” between theoptical disc 13 and the track buffer memory 19 on a time sharing basisand at a predetermined constant transfer rate Rp. The predeterminedconstant transfer rate Rp is equal to, for example, 25 Mbps.

[0130] The first information signal “A” is transferred between the trackbuffer memory 19 and the audio-video encoding and decoding unit 20 at atransfer rate Ra selected from among predetermined values. All thepredetermined values are lower than the predetermined constant transferrate Rp related to the optical head 14. The second information signal“B” is transferred between the track buffer memory 19 and theaudio-video encoding and decoding unit 20 at a transfer rate Rbchangeable among the predetermined values.

[0131] As will be mentioned later, the apparatus 10A can substantiallycontinuously and simultaneously record or reproduce the firstinformation signal “A” and the second information signal “B”.

[0132] In more detail, each of the transfer rates Ra and Rb is selectedfrom among a value of 8 Mbps which corresponds to a recording time of 2hours and a high picture quality, a value of 4 Mbps which corresponds toa recording time of 4 hours and a slightly high picture quality, and avalue of 2 Mbps which corresponds to a recording time of 8 hours and anormal picture quality. Ones of these values can be designated asdesired values of the transfer rates Ra and Rb according to user'soperation of the key input unit 23 (see FIG. 1). A value of 17 Mbps maybe added to the candidate values. During the recording of the firstinformation signal “A” and the second information signal “B” on theoptical disc 13, the transfer rates Ra and Rb are set to the desiredvalues designated by user's operation of the key input unit 23. Duringthe reproduction of the first information signal “A” and the secondinformation signal “B” from the optical disc 13, information ofrecording compression rates is derived from control data for theinformation signals “A” and “B”, and the transfer rates Ra and Rb areset in response to the recording compression rates. Alternatively,during the reproduction of the first information signal “A” and thesecond information signal “B” from the optical disc 13, control data(management information) representative of transfer rates Ra and Rb usedin the recording are reproduced from the optical disc 13, and thereproduction transfer rates Ra and Rb are set in accordance with thereproduced control data.

[0133] The system controller 22 (see FIG. 1) controls the track buffermemory 19 via the signal processor 18 (see FIG. 1). The systemcontroller 22 virtually divides or partitions the track buffer memory 19into the first and second areas 19 a and 19 b. Specifically, the systemcontroller 22 sets the first and second areas 19 a and 19 b in the trackbuffer memory 19 in response to the values of the transfer rates Ra andRb. The ratio in capacity between the first and second areas 19 a and 19b depends on the ratio “Ra:Rb”, that is, the ratio between the transferrates Ra and Rb. Regarding the first area 19 a in the track buffermemory 19, the system controller 22 sets an empty value and a full valuein response to the value of the transfer rate Ra. The empty valuecorresponds to a slightly occupied state or a substantially empty stateof the first area 19 a. The full value corresponds to a fully occupiedstate of the first area 19 a. Regarding the second area 19 b in thetrack buffer memory 19, the system controller 22 sets an empty value anda full value in response to the value of the transfer rate Rb. The emptyvalue corresponds to a slightly occupied state or a substantially emptystate of the second area 19 b. The full value corresponds to a fullyoccupied state of the second area 19 b. The system controller 22 alwaysmonitors the degree of occupancy of each of the first and second areas19 a and 19 b which varies between the related empty value and therelated full value under normal conditions.

[0134] Alternatively, the division of the track buffer memory 19 intothe first and second areas 19 a and 19 b may be responsive to the typeof the mode of operation of the apparatus 10A. For example, in the caseof the operation mode during which the apparatus 10A reproduces one ofthe information signals “A” and “B” and records the other informationsignal, greater one of the first and second areas 19 a and 19 b isassigned to the information signal to be recorded while smaller one isassigned to the reproduced information signal. This design reliablyprevents the occurrence of an interruption of the continuously recordingof the information signal. The system controller 22 implements thedivision of the track buffer memory 19 into the first and second areas19 a and 19 b when receiving a recording start command signal or aplayback start command signal. Preferably, the system controller 22implements the division of the track buffer memory 19 after confirmingthe absence of data from the track buffer memory 19 which are beingreproduced or recorded.

[0135] Two-Signal Playback Mode

[0136]FIG. 3 shows a portion of the apparatus 10A which is operating ina two-signal playback mode. The amplifier unit 16 and the signalprocessor 18 are omitted from FIG. 3 for a better understanding. Withreference to FIG. 3, the optical disc 13 is designed exclusively forplayback. The optical disc 13 has the first areas 13 a on which theblocks of the first information signal “A” are previously recordedrespectively. In addition, the optical disc 13 has the second areas 13 bon which the blocks of the second information signal “B” are previouslyrecorded respectively. Each of the blocks of the first informationsignal “A” has a predetermined size (a predetermined total number ofbits) Ya. Each of the blocks of the second information signal “B” has apredetermined size (a predetermined total number of bits) Yb equal to ordifferent from the predetermined size Ya.

[0137] As shown in FIG. 4, the first areas 13 a of the optical disc 13are given addresses A1, A2, A3, . . . , respectively. Thus, the firstareas 13 a are also referred to as the first areas A1, A2, A3, . . . .The blocks of the first information signal “A” are recorded on the firstareas A1, A2, A3, . . . , respectively. Preferably, the size Ya of theblocks of the first information signal “A” is equal to the size of thefirst areas A1, A2, A3, . . . . The placement of the first areas 13 a isdesigned to meet requirements for a seek time. As shown in FIG. 5, thesecond areas 13 b of the optical disc 13 are given addresses B 1, B2,B3, . . . , respectively. Thus, the second areas 13 b are also referredto as the second areas B1, B2, B3, . . . . The blocks of the secondinformation signal “B” are recorded on the second areas B1, B2, B3, . .. , respectively. Preferably, the size Yb of the blocks of the secondinformation signal “B” is equal to the size of the second areas B1, B2,B3, . . . . The placement of the second areas 13 b is designed to meetrequirements for a seek time. First, a block of the first informationsignal “A” is reproduced from first one Al (the first area 13 a giventhe address A1) of the first areas 13 a. Second, a block of the secondinformation signal “B” is reproduced from first one B1 (the second area13 b given the address B1) of the second areas 13 b. The first area A1and the second area B1 are located relative to each other so that theoptical head 14 can move therebetween in a predetermined time (equal to,for example, 1.5 seconds). Therefore, the maximum seek time during whichthe optical head 14 moves between the first area 13 a and the secondarea 13 b is equal to the predetermined time (for example, 1.5 seconds).

[0138] During the two-signal playback mode of operation of the apparatus10A, the optical head 14 moves to a position of a designated track onthe optical disc 13 and waits for a start sector. Then, the optical head14 meets the start sector, and the reproduction of the first informationsignal “A” and the second information signal “B” is started. The systemcontroller 22 derives information of recording compression rates(information of transfer rates Ra and Rb) from control data for thereproduced information signals “A” and “B”. The system controller 22divides or partitions the track buffer memory 19 into a first area 19 aand a second area 19 b, and sets capacities of the first and secondareas 19 a and 19 b in response to the recording compression rates. Inaddition, the system controller 22 sets empty values and full values ofthe first and second areas 19 a and 19 b in response to the recordingcompression rates.

[0139] The optical head 14 alternately reproduces the first informationsignal “A” and the second information signal “B” from the first areas 13a and the second areas 13 b of the optical disc 13 on a time sharingbasis. The reproduced first information signal “A” is stored into thefirst area 19 a of the track buffer memory 19 from the optical head 14at a predetermined constant transfer rate Rp (equal to, for example, 25Mbps). The reproduced second information signal “B” is stored into thesecond area 19 b of the track buffer memory 19 from the optical head 14at the predetermined constant transfer rate Rp. Storing the reproducedfirst information signal “A” into the first area 19 a of the trackbuffer memory 19 alternates with storing the reproduced secondinformation signal “B” into the second area 19 b of the track buffermemory 19.

[0140] The system controller 22 sets transfer rates Ra and Rb for thefirst information signal “A” and the second information signal “B” onthe basis of the recording compression rates. The transfer rates Ra andRb are lower than the predetermined constant transfer rate Rp. The firstinformation signal “A” is transmitted from the first area 19 a of thetrack buffer memory 19 to the audio-video encoding and decoding unit 20at the transfer rate Ra. The second information signal “B” istransmitted from the second area 19 b of the track buffer memory 19 tothe audio-video encoding and decoding unit 20 at the transfer rate Rb.Generally, the transmission of the first information signal “A” from thetrack buffer memory 19 and the transmission of the second informationsignal “B” from the track buffer memory 19 are implemented on a timesharing basis. The audio-video encoding and decoding unit 20 expands anddecodes the first information signal “A” into a first non-compressedinformation signal “A”. In addition, the audio-video encoding anddecoding unit 20 expands and decodes the second information signal “B”into a second non-compressed information signal “B”. The firstnon-compressed information signal “A” and the second non-compressedinformation signal “B” are transmitted from the audio-video encoding anddecoding unit 20 to a display and a loudspeaker, being simultaneouslyconverted into corresponding pictures and sounds.

[0141] The system controller 22 operates in accordance with a programstored in its internal ROM. FIG. 6 is a flowchart of a segment of theprogram which relates to the two-signal playback mode of operation ofthe apparatus 10A. The program segment in FIG. 6 is started in responseto a two-signal-playback start command signal fed from the key inputunit 23.

[0142] With reference to FIG. 6, a first step S32 of the program segmentdecides whether or not the optical head 14 has reached a target positionon the optical disc 13. Initially, the target position corresponds tofirst one A1 of the first areas 13 a in the optical disc 13. When theoptical head 14 has not reached the target position yet, the step S32 isrepeated. When the optical head 14 has reached the target position, theprogram advances from the step S32 to a step S33.

[0143] The step S33 enables the optical head 14 to reproduce the firstinformation signal “A” from the present first area 13 a in the opticaldisc 13. The step S33 stores the reproduced first information signal “A”into the first area 19 a in the track buffer memory 19 at thepredetermined constant transfer rate Rp.

[0144] A step S34 following the step S33 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related empty value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S34 to thestep S33. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S34 to a step S35.

[0145] The step S35 transfers the first information signal “A” from thefirst area 19 a in the track buffer memory 19 to the audio-videoencoding and decoding unit 20 at the transfer rate Ra.

[0146] A step S36 following the step S35 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related full value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S36 to thestep S35. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S36 to a step S37.

[0147] The step S37 forces the optical head 14 to suspend thereproduction of the first information signal “A” from the present firstarea 13 a in the optical disc 13.

[0148] A step S38 subsequent to the step S37 moves the optical head 14toward a next target position. The next target position corresponds to,for example, first one B1 of the second areas 13 b in the optical disc13. After the step S38, the program advances to a step S39.

[0149] The step S39 decides whether or not the optical head 14 hasreached the target position on the optical disc 13. When the opticalhead 14 has not reached the target position yet, the step S39 isrepeated. When the optical head 14 has reached the target position, theprogram advances from the step S39 to a step S40.

[0150] In this way, the optical head 14 moves from the first area 13 ato the second area 13 b in the optical disc 13. The seek time Tabrelated to this movement of the optical head 14 is equal to 1.5 secondsor shorter.

[0151] The step S40 enables the optical head 14 to reproduce the secondinformation signal “B” from the present second area 13 b in the opticaldisc 13. The step S40 stores the reproduced second information signal“B” into the second area 19 b in the track buffer memory 19 at thepredetermined constant transfer rate Rp.

[0152] A step S41 following the step S40 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related empty value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S41 to thestep S40. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S41 to a step S42.

[0153] The step S42 transfers the second information signal “B” from thesecond area 19 b in the track buffer memory 19 to the audio-videoencoding and decoding unit 20 at the transfer rate Rb.

[0154] A step S43 following the step S42 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related full value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S43 to thestep S42. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S43 to a step S44.

[0155] The step S44 forces the optical head 14 to suspend thereproduction of the second information signal “B” from the presentsecond area 13 b in the optical disc 13.

[0156] A step S45 subsequent to the step S44 moves the optical head 14toward a next target position. The next target position corresponds to,for example, second one A2 of the first areas 13 a in the optical disc13. After the step S45, the program returns to the step S32.

[0157] Thus, the optical head 14 moves from the second area 13 b to thefirst area 13 a in the optical disc 13. The seek time Tba related tothis movement of the optical head 14 is equal to 1.5 seconds or shorter.

[0158] During the repetitive execution of the program segment in FIG. 6,the target position of the optical head 14 is sequentially set intocorrespondence with the first and second areas A1, B1, A2, B2, A3, B3, .. . in the optical disc 13. Therefore, the optical head 14 alternatelyreproduces the first information signal “A” and the second informationsignal “B” from the first and second areas 13 a and 13 b of the opticaldisc 13 in the order as “A1, B1, A2, B2, A3, B3, . . . ”.

[0159] Preferably, the step S37 or the step S44 is followed by a stepwhich decides whether or not both the reproduction of the firstinformation signal “A” from the optical disc 13 and the reproduction ofthe second information signal “B” therefrom are required to besuspended. In this case, when both the reproduction of the firstinformation signal “A” from the optical disc 13 and the reproduction ofthe second information signal “B” therefrom are required to besuspended, the optical head 14 is controlled to implement the requiredsuspension of reproduction.

[0160] With reference to FIG. 7, after the degree of occupancy of thefirst area 19 a in the track buffer memory 19 reaches the related emptyvalue, the first information signal “A” is read out from the memory area19 a at the transfer rate Ra and the first information signal “A” istransmitted from the first area Al in the optical disc 13 to the memoryarea 19 a at the predetermined constant transfer rate Rp. Thus, duringthis stage, the degree of occupancy of the memory area 19 a increases ata rate corresponding to “Rp−Ra”.

[0161] When the degree of occupancy of the memory area 19 a reaches therelated full value, the transmission of the first information signal “A”from the first area A1 in the optical disc 13 to the memory area 19 a issuspended. Then, the optical head 14 is moved to a positioncorresponding to the second area B1 in the optical disc 13. The seektime Tab related to this movement of the optical head 14 is equal to orshorter than 1.5 seconds. The optical head 14 transmits the secondinformation signal “B” from the second area B1 in the optical disc 13 tothe second area 19 b of the track buffer memory 19 at the predeterminedconstant transfer rate Rp. Even after the degree of occupancy of thememory area 19 a reaches the related full value, the first informationsignal “A” continues to be read out from the memory area 19 a at thetransfer rate Ra. Thus, during this stage, the degree of occupancy ofthe memory area 19 a decreases at a rate corresponding to “Ra”. Theread-out of the first information signal “A” from the memory area 19 ais completed before the optical head 14 accesses the first area A2 inthe optical disc 13.

[0162] After the degree of occupancy of the second area 19 b in thetrack buffer memory 19 reaches the related empty value, the secondinformation signal “B” is read out from the memory area 19 b at thetransfer rate Rb and the second information signal “B” continues to betransmitted from the second area B1 in the optical disc 13 to the memoryarea 19 b at the predetermined constant transfer rate Rp. Thus, duringthis stage, the degree of occupancy of the memory area 19 b increases ata rate corresponding to “Rp−Rb”.

[0163] When the degree of occupancy of the memory area 19 b reaches therelated full value, the transmission of the second information signal“B” from the second area B1 in the optical disc 13 to the memory area 19b is suspended. Then, the optical head 14 is moved to a positioncorresponding to the first area A2 in the optical disc 13. The seek timeTba related to this movement of the optical head 14 is equal to orshorter than 1.5 seconds. The optical head 14 transmits the firstinformation signal “A” from the first area A2 in the optical disc 13 tothe first area 19 a of the track buffer memory 19 at the predeterminedconstant transfer rate Rp. Even after the degree of occupancy of thememory area 19 b reaches the related full value, the second informationsignal “B” continues to be read out from the memory area 19 b at thetransfer rate Rb. Thus, during this stage, the degree of occupancy ofthe memory area 19 b decreases at a rate corresponding to “Rb”. Theread-out of the second information signal “B” from the memory area 19 bis completed before the optical head 14 accesses the second area B2 inthe optical disc 13.

[0164] As previously indicated, the rate of the transfer of the firstand second information signals “A” and “B” by the optical head 14 isdenoted by “Rp” (Mbps). The rate of the transfer of the firstinformation signal “A” from the track buffer memory 19 is denoted by“Ra” (Mbps). The rate of the transfer of the second information signal“B” from the track buffer memory 19 is denoted by “Rb” (Mbps). Theminimum capacity of the track buffer memory 19 is denoted by “Ym”(Mbits). The size (the total number of bits) of the first informationsignal “A” recorded on each of the first areas A1, A2, A3, . . . in theoptical disc 13 is denoted by “Ya” (Mbits). The size (the total numberof bits) of the second information signal “B” recorded on each of thesecond areas B1, B2, B3, . . . in the optical disc 13 is denoted by “Yb”(Mbits). The seek time of movement of the optical head 14 from a firstarea 13 a to a second area 13 b in the optical disc 13 is denoted by“Tab” (s). The seek time of movement of the optical head 14 from asecond area 13 b to a first area 13 a in the optical disc 13 is denotedby “Tba” (s).

[0165] The seek time Tab is equal to a first time interval plus a secondtime interval. The first time interval starts from the moment at whichthe optical head 14 reaches a reproduction end position and suspends thereproduction of the first information signal “A” from the first area 13a of the optical disc 13. The first time interval ends and the secondtime interval starts when the optical head 14 moves to the second area13 b of the optical disc 13. The second time interval continues untilthe optical head 14 starts reproducing the second information signal “B”from the second area 13 b of the optical disc 13. During the second timeinterval, a target address of the second area 13 b of the optical disc13 is found, and preparations for the reproduction of the secondinformation signal “B” therefrom have been made.

[0166] Similarly, the seek time Tba is equal to a first time intervalplus a second time interval. The first time interval starts from themoment at which the optical head 14 reaches a reproduction end positionand suspends the reproduction of the second information signal “B” fromthe second area 13 b of the optical disc 13. The first time intervalends and the second time interval starts when the optical head 14 movesto the first area 13 a of the optical disc 13. The second time intervalcontinues until the optical head 14 starts reproducing the firstinformation signal “A” from the first area 13 a of the optical disc 13.During the second time interval, a target address of the first area 13 aof the optical disc 13 is found, and preparations for the reproductionof the first information signal “A” therefrom have been made.

[0167] The mean value of the rate Ra of the transfer of the firstinformation signal “A” from the first area 19 a of the track buffermemory 19 plus the mean value of the rate Rb of the transfer of thesecond information signal “B” from the second area 19 b of the trackbuffer memory 19 equals smaller than the rate Rp of the transfer of thefirst and second information signals “A” and “B” to the track buffermemory 19. Thus, the transfer rates Rp, Ra, and Rb are in the followingrelation.

Rp>Ra+Rb  (1)

[0168] The playback time Ta (S) for which the optical head 14continuously reproduces the first information signal “A” from theoptical disc 13 is given as follows.

Ta=Ya/Rp  (2)

[0169] The playback time Tb (S) for which the optical head 14continuously reproduces the second information signal “B” from theoptical disc 13 is given as follows.

Tb=Yb/Rp  (3)

[0170] Regarding the transfer rates Rp, Ra, and Rb, the following ratiois considered.

Rp/(Rp−Ra−Rb)  (4)

[0171] where “Rp” corresponds to a 1-cycle time during which the firstand second information signals “A” and “B” are sequentially reproducedonce, and “(Rp−Ra−Rb)” corresponds to a seek period in the 1-cycle time.

[0172] Regarding the times Ta, Tab, Tb, and Tba, the following ratio isconsidered.

(Ta+Tab+Tb+Tba)/(Tab+Tba)  (5)

[0173] where “(Ta+Tab+Tb+Tba)” corresponds to a 1-cycle time duringwhich the first and second information signals “A” and “B” aresequentially reproduced once, and “(Tab+Tba)” corresponds to a totalseek period in the 1-cycle time.

[0174] The ratio in the relation (4) and the ratio in the relation (5)are equal to each other, and the following equation is available.

Rp/(Rp−Ra−Rb)=(Ta+Tab+Tb+Tba)/(Tab+Tba)  (6)

[0175] The equation (6) is changed into the following version.

(Ta+Tb)=(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)  (7)

[0176] Combining the equations (2) and (3) with the equation (7) resultsin the following equation.

(Ya+Yb)=Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)  (8)

[0177] The rate Rp of the transfer of the first and second informationsignals “A” and “B” from the optical disc 13 to the track buffer memory19 is equal to the predetermined constant value. The rates Ra and Rb ofthe transfer of the first and second information signals “A” and “B”from the track buffer memory 19 are decided on the basis of theconditions of recording the first and second information signals “A” and“B” on the optical disc 13. The seek times Tab and Tba are decidedaccording to the specifications of the apparatus 10A and the addresseson the optical disc 13. To implement continuous playback regarding boththe first and second information signals “A” and “B”, the size (thetotal number of bits) Ya of the first information signal “A” on each ofthe first areas 13 a of the optical disc 13 and the size (the totalnumber of bits) Yb of the second information signal “B” on each of thesecond areas 13 b of the optical disc 13 are chosen to satisfy relations(9), (10), and (11) as follows.

(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)  (9)

Ya≧Rp·Ra·(Tab+Tba)/(Rp−Ra−Rb)  (10)

Yb≧Rp·Rb·(Tab+Tba)/(Rp−Ra−Rb)  (11)

[0178] During the two-signal playback mode of operation of the apparatus10A, the first information signal “A” is continuously transferred fromone of the first areas 13 a of the optical disc 13 to the first area 19a of the track buffer memory 19 before the second information signal “B”is continuously transferred from one of the second areas 13 b of theoptical disc 13 to the second area 19 b of the track buffer memory 19.The first and second information signals “A” and “B” are continuouslytransferred from the first and second areas 19 a and 19 b of the trackbuffer memory 19 to the audio-video encoding and decoding unit 20. Toenable the audio-video encoding and decoding unit 20 to continuouslyrecover the contents of the first and second information signals “A” and“B”, the size (the total number of bits) Ya of the first informationsignal “A” on each of the first areas 13 a of the optical disc 13 andthe size (the total number of bits) Yb of the second information signal“B” on each of the second areas 13 b of the optical disc 13 are chosento satisfy the above-indicated relations (9), (10), and (11) while therelation among the transfer rates Ra and Rb and the seek times Tab andTba is taken into consideration.

[0179] In addition, the maximum size of the track buffer memory 19, andthe empty value and the full value related to each of the first andsecond areas 19 a and 19 b in the track buffer memory 19 are decidedaccording to the relations (9), (10), and (11).

[0180] The minimum capacity Ym of the track buffer memory 19 satisfiesone of the following relations (12) and (13).

Ym>(Tb+Tab+Tba)·Ra+(Ta+Tab+Tba)·Rb  (12)

Ym>Ta·(Rp−Ra)+Tb·(Rp−Rb)  (13)

[0181] Combining the equations and relations (2), (3), (10), and (11)with the relations (12) and (13) result in the following relation.

Ym>{(Rp−Ra)·Ra+(Rp−Rb)·Rb}·(Tab+Tba)/(Rp−Ra−Rb)  (14)

[0182] The term “(Rp−Ra)·Ra·(Tab+Tba)/(Rp−Ra−Rb)” in the relation (14)means a first memory-size reference value for the first informationsignal “A”. Similarly, the term “(Rp−Rb)·Rb·(Tab+Tba)/(Rp−Ra−Rb)” in therelation (14) means a second memory-size reference value for the secondinformation signal “B”. According to the relation (14), it is preferablethat the size of the first area 19 a of the track buffer memory 19 forthe first information signal “A” is set greater than the firstmemory-size reference value, and that the related empty value and therelated full value are decided in view of the setting of the size of thefirst memory area 19 a. Similarly, it is preferable that the size of thesecond area 19 b of the track buffer memory 19 for the secondinformation signal “B” is set greater than the second memory-sizereference value, and that the related empty value and the related fullvalue are decided in view of the setting of the size of the secondmemory area 19 b.

[0183] To provide a small margin for more reliably implementingcontinuous playback of the contents of the first and second informationsignals “A” and “B”, the minimum capacity Ym of the track buffer memory19 satisfies the following relation.

Ym>(Ta+Tb+Tab+Tba)·(Ra+Rb)  (15)

[0184] In the case where the seek times Tab and Tba are set to a samefixed value T, the relation (15) is rewritten as follows.

Ym>(Ta+Tb+2T)·(Ra+Rb)  (16)

[0185] To provide a system margin for allowing a retry process and ashock-proof memory function, it is preferable that the minimum capacityYm of the track buffer memory 19 exceeds the value defined by theright-hand side of the relation (16).

[0186] Accordingly, it is more preferable that the size of the firstarea 19 a of the track buffer memory 19 for the first information signal“A” is set greater than the value “(Ta+Tb+2T)·Ra”, and that the relatedempty value and the related full value are decided in view of thesetting of the size of the first memory area 19 a. Similarly, it is morepreferable that the size of the second area 19 b of the track buffermemory 19 for the second information signal “B” is set greater than thevalue “(Ta+Tb+2T)·Rb”, and that the related empty value and the relatedfull value are decided in view of the setting of the size of the secondmemory area 19 b.

[0187] Combining the equations (2) and (3) and the relation (9) with therelation (15) results in the following relation.

Ym>Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)  (17)

[0188] In the case where the seek times Tab and Tba are set to the samefixed value T, the relation (17) is rewritten as follows.

Ym>2·Rp·(Ra+Rb)·T/(Rp−Ra−Rb)  (18)

[0189] To provide a system margin for allowing a retry process and ashock-proof memory function, it is preferable that the minimum capacityYm of the track buffer memory 19 exceeds the value defined by theright-hand side of the relation (18).

[0190] Accordingly, it is more preferable that the size of the firstarea 19 a of the track buffer memory 19 for the first information signal“A” is set greater than the value “Rp·Ra·(Tab+Tba)/(Rp−Ra−Rb)”, and thatthe related empty value and the related full value are decided in viewof the setting of the size of the first memory area 19 a. Similarly, itis more preferable that the size of the second area 19 b of the trackbuffer memory 19 for the second information signal “B” is set greaterthan the value “Rp·Rb·(Tab+Tba)/(Rp−Ra−Rb)”, and that the related emptyvalue and the related full value are decided in view of the setting ofthe size of the second memory area 19 b.

[0191] It should be noted that a portion of the buffer memory 21connected to the audio-video encoding and decoding unit 20 may be usedas a track buffer memory substituting for the track buffer memory 19.

[0192] The track buffer memory 19 absorbs the differences between thepredetermined constant transfer rate Rp and the transfer rates Ra andRb, that is, the differences between the reproduced-signal transfer ratedetermined by the optical head 14 and the transfer rates related to theexpansion-resultant information signals (the expansion-resultantaudio-video signals). In a preferable way, two basic areas for the firstinformation signal “A” and the second information signal “B” areprovided in the track buffer memory 19, and the remaining area of thetrack buffer memory 19 is divided into two portions assigned to thefirst information signal “A” and the second information signal “B”respectively. The division-resultant two portions are referred to asadditive areas. One basic area plus one additive area are assigned tothe first information signal “A”. Similarly, one basic area plus oneadditive area are assigned to the second information signal “B”. Theratio in size between the additive areas is substantially equal to thatbetween the basic areas. The additive areas provide margins to trackbuffers for the first and second information signals “A” and “B”,respectively.

[0193] For example, the first area 19 a and the second area 19 b areprovided in the track buffer memory 19 as follows. In the case where thetransfer rate Ra for the first information signal “A” is set to 8 Mbps,a first basic area of 32 Mbits for the first information signal “A” isprovided in the track buffer memory 19. In the case where the transferrate Rb for the second information signal “B” is set to 4 Mbps, a secondbasic area of 16 Mbits for the second information signal “B” is providedin the track buffer memory 19. The remaining 16-Mbit area of the trackbuffer memory 19 is divided into a first portion (a first additive area)of about 10 Mbits and a second portion (a second additive area) of about5 Mbits. The first basic area and the first additive area are combinedinto the first memory area 19 a for the first information signal “A”.The first memory area 19 a has a size of about 42 Mbits. The secondbasic area and the second additive area are combined into the secondmemory area 19 b for the second information signal “B”. The secondmemory area 19 b has a size of about 21 Mbits. This memory divisionenables the track buffer memory 19 to be efficiently used.

[0194] The system controller 22 provides the first and second areas 19 aand 19 b in the track buffer memory 19 in response to thetwo-signal-playback start command signal and the information of thetransfer rates Ra and Rb. During a one-signal playback mode of operationof the apparatus 10A, the track buffer memory 19 is used as anon-partitioned 64-Mbit memory. Thus, during the one-signal playbackmode of operation of the apparatus 10A, the playability including theretry performance can be enhanced. Preferably, the system controller 22checks data in the track buffer memory 19 when receiving thetwo-signal-playback start command signal. The system controller 22implements the division of the track buffer memory 19 into the first andsecond areas 19 a and 19 b after confirming the absence of data from thetrack buffer memory 19 which are being reproduced or recorded. Duringthe two-signal playback mode of operation of the apparatus 10A, when thetransfer rates Ra and Rb for the information signals “A” and “B” arechanged, the system controller 22 checks data in the track buffer memory19. In this case, the system controller 22 redivides the track buffermemory 19 after confirming the absence of data from the track buffermemory 19 which are being reproduced or recorded. Thus, the margins ofthe track buffer memory 19 remains optimized even when the transferrates Ra and Rb for the information signals “A” and “B” are changed.

[0195] Preferably, the maximum values Tmax of the seek times Tab and Tbarelated to the optical head 14 are equal to each other. The maximum seektime Tmax is equal to, for example, 1.5 seconds. When the maximum seektime Tmax is used for the seek times Tab and Tba, thepreviously-indicated relation (9) is changed into the following version.

(Ya+Yb)≧Rp·(Ra+Rb)·2·Tmax/(Rp−Ra−Rb)  (19)

[0196] When the maximum seek time Tmax is equal to 1.5 seconds, therelation (19) is rewritten as follows.

(Ya+Yb)≧3·Rp·(Ra+Rb)/(Rp−Ra−Rb)  (20)

[0197] Preferably, the size (the total number of bits) Ya of the firstinformation signal “A” on each of the first areas 13 a of the opticaldisc 13 and the size (the total number of bits) Yb of the secondinformation signal “B” on each of the second areas 13 b of the opticaldisc 13 are chosen to satisfy the relation (19) or (20).

[0198] Two-Signal Recording Mode

[0199]FIG. 8 shows a portion of the apparatus 10A which is operating ina two-signal recording mode. The amplifier unit 16 and the signalprocessor 18 are omitted from FIG. 8 for a better understanding. Withreference to FIG. 8, the first information signal “A” is transmittedfrom the audio-video encoding and decoding unit to the first area 19 ain the track buffer memory 19 at the first transfer rate Ra. The secondinformation signal “B” is transmitted from the audio-video encoding anddecoding unit 20 to the second area 19 b in the track buffer memory 19at the second transfer rate Rb. Generally, the transmission of the firstinformation signal “A” to the track buffer memory 19 and thetransmission of the second information signal “B” to the track buffermemory 19 are implemented on a time sharing basis. The first informationsignal “A” is transmitted from the first area 19 a in the track buffermemory 19 to the optical head 14 at the predetermined constant transferrate Rp. The second information signal “B” is transmitted from thesecond area 19 b in the track buffer memory 19 to the optical head 14 atthe predetermined constant transfer rate Rp. The optical head 14 recordsthe first information signal “A” and the second information signal “B”on the first area 13 a and the second area 13 b of the optical disc 13respectively on a time sharing basis and at the predetermined constanttransfer rate Rp. The predetermined constant transfer rate Rp is higherthan the first and second transfer rates Ra and Rb.

[0200] The optical disc 13 is of the rewritable type. The optical disc13 is previously provided with the first areas 13 a for storing therespective blocks of the first information signal “A”. In addition, theoptical disc 13 is previously provided with the second areas 13 b forstoring the respective blocks of the second information signal “B”. Thesecond areas 13 b are separate from the first areas 13 a.

[0201] The first areas 13 a in the optical disc 13 are given addressesA1, A2, A3, . . . , respectively (see FIG. 4). Thus, the first areas 13a are also referred to as the first areas A1, A2, A3, . . . . The blocksof the first information signal “A” are recorded on the first areas A1,A2, A3, . . . , respectively. Preferably, the size Ya of the blocks ofthe first information signal “A” is equal to the size of the first areasA1, A2, A3, . . . . The placement of the first areas 13 a is designed tomeet requirements for a seek time. The second areas 13 b in the opticaldisc 13 are given addresses B1, B2, B3, . . . , respectively (see FIG.5). Thus, the second areas 13 b are also referred to as the second areasB1, B2, B3, . . . . The blocks of the second information signal “B” arerecorded on the second areas B1, B2, B3, . . . , respectively.Preferably, the size Yb of the blocks of the second information signal“B” is equal to the size of the second areas B1, B2, B3, . . . . Theplacement of the second areas 13 b is designed to meet the requirementsfor a seek time. First, a block of the first information signal “A” isrecorded on the first area A1 (the first area 13 a given the addressA1). Second, a block of the second information signal “B” is recorded onthe second area B1 (the second area 13 b given the address B1). Thefirst area A1 and the second area B1 are located relative to each otherso that the optical head 14 can move therebetween in a predeterminedtime (equal to, for example, 1.5 seconds). Therefore, the maximum seektime during which the optical head 14 moves between the first area 13 aand the second area 13 b is equal to the predetermined time (forexample, 1.5 seconds).

[0202] During the two-signal recording mode of operation of theapparatus 10A, the audio-video encoding and decoding unit 20 encodesoriginal information signals into the first and second informationsignals “A” and “B” respectively. The first and second informationsignals “A” and “B” are transferred from the audio-video encoding anddecoding unit 20 to the track buffer memory 19 at the rates Ra and Rbrespectively. The rates Ra and Rb of the transfer of the first andsecond information signals “A” and “B” from the audio-video encoding anddecoding unit 20 to the track buffer memory 19 can be selected fromamong different values according to user's operation of the key inputunit 23 (see FIG. 1). The different values include a transfer rate of 8Mbps which corresponds to a recording time of 2 hours and a high picturequality, a transfer rate of 4 Mbps which corresponds to a recording timeof 4 hours and a slightly high picture quality, and a transfer rate of 2Mbps which corresponds to a recording time of 8 hours and a normalpicture quality. A transfer rate of 17 Mbps may be added to thecandidate values. The first and second information signals “A” and “B”are temporarily stored in the first and second areas 19 a and 19 b ofthe track buffer memory 19. At an initial stage, the optical head 14 isin a stand-by state or a kick wait state while being located at aposition corresponding to a target track on the optical disc 13. Thesystem controller 22 always monitors the degree of occupancy of each ofthe first and second memory areas 19 a and 19 b which varies between therelated empty value and the related full value under normal conditions.When the degrees of occupancy of the first and second memory areas 19 aand 19 b reach the related full values, the first and second informationsignals “A” and “B” start to be alternately read out from the first andsecond memory areas 19 a and 19 b on a time sharing basis and at thepredetermined constant transfer rate Rp. The optical head 14 alternatelyrecords the readout first information signal “A” and the read-out secondinformation signal “B” on the first areas 13 a and the second areas 13 bof the optical disc 13 respectively on a time sharing basis and at thepredetermined constant transfer rate Rp. In this way, the continuouslyand simultaneously recording of the original information signals isimplemented.

[0203] The system controller 22 operates in accordance with the programstored in its internal ROM. FIG. 9 is a flowchart of a segment of theprogram which relates to the two-signal recording mode of operation ofthe apparatus 10A. The program segment in FIG. 9 is started in responseto a two-signal-recording start command signal fed from the key inputunit 23.

[0204] With reference to FIG. 9, a first step S52 of the program segmentdecides whether or not the optical head 14 has reached a target positionon the optical disc 13. Initially, the target position corresponds tofirst one A1 of the first areas 13 a in the optical disc 13. When theoptical head 14 has not reached the target position yet, the step S52 isrepeated. When the optical head 14 has reached the target position, theprogram advances from the step S52 to a step S53.

[0205] The step S53 stores the first information signal “A”, which isoutputted from the audio-video encoding and decoding unit 20, into thefirst area 19 a in the track buffer memory 19 at the transfer rate

[0206] A step S54 following the step S53 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related full value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S54 to thestep S53. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S54 to a step S55.

[0207] The step S55 transfers the first information signal “A” from thefirst area 19 a in the track buffer memory 19 to the optical head 14 atthe predetermined constant transfer rate Rp. The step S55 enables theoptical head 14 to record the first information signal “A” on thepresent first area 13 a in the optical disc 13 at the predeterminedconstant transfer rate Rp.

[0208] A step S56 following the step S55 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related empty value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S56 to thestep S55. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S56 to a step S57.

[0209] The step S57 forces the optical head 14 to suspend the recordingof the first information signal “A” on the present first area 13 a inthe optical disc 13.

[0210] A step S58 subsequent to the step S57 moves the optical head 14toward a next target position. The next target position corresponds to,for example, first one B1 of the second areas 13 b in the optical disc13. After the step S58, the program advances to a step S59.

[0211] The step S59 decides whether or not the optical head 14 hasreached the target position on the optical disc 13. When the opticalhead 14 has not reached the target position yet, the step S59 isrepeated. When the optical head 14 has reached the target position, theprogram advances from the step S59 to a step S60.

[0212] In this way, the optical head 14 moves from the first area 13 ato the second area 13 b in the optical disc 13. The seek time Tabrelated to this movement of the optical head 14 is equal to 1.5 secondsor shorter.

[0213] The step S60 stores the second information signal “B”, which isoutputted from the audio-video encoding and decoding unit 20, into thesecond area 19 b in the track buffer memory 19 at the transfer rate Rb.

[0214] A step S61 following the step S60 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related full value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S61 to thestep S60. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S61 to a step S62.

[0215] The step S62 transfers the second information signal “B” from thesecond area 19 b in the track buffer memory 19 to the optical head 14 atthe predetermined constant transfer rate Rp. The step S62 enables theoptical head 14 to record the second information signal “B” on thepresent second area 13 b in the optical disc 13 at the predeterminedconstant transfer rate Rp.

[0216] A step S63 following the step S62 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related empty value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S63 to thestep S62. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S63 to a step S64.

[0217] The step S64 forces the optical head 14 to suspend the recordingof the second information signal “B” on the present second area 13 b inthe optical disc 13.

[0218] A step S65 subsequent to the step S64 moves the optical head 14toward a next target position. The next target position corresponds to,for example, second one A2 of the first areas 13 a in the optical disc13. After the step S65, the program returns to the step S52.

[0219] Thus, the optical head 14 moves from the second area 13 b to thefirst area 13 a in the optical disc 13. The seek time Tba related tothis movement of the optical head 14 is equal to 1.5 seconds or shorter.

[0220] During the repetitive execution of the program segment in FIG. 9,the target position of the optical head 14 is sequentially set intocorrespondence with the first and second areas A1, B1, A2, B2, A3, B3, .. . in the optical disc 13. Therefore, the optical head 14 alternatelyrecords the first information signal “A” and the second informationsignal “B” on the first and second areas 13 a and 13 b of the opticaldisc 13 in the order as “A1, B1, A2, B2, A3, B3, . . . ”.

[0221] Preferably, the step S57 or the step S64 is followed by a stepwhich decides whether or not both the recording of the first informationsignal “A” on the optical disc 13 and the recording of the secondinformation signal “B” thereon are required to be suspended. In thiscase, when both the recording of the first information signal “A” on theoptical disc 13 and the recording of the second information signal “B”thereon are required to be suspended, the optical head 14 is controlledto implement the required suspension of recording.

[0222] It is preferable to provide the optical disc 13 with a managementarea separate from the first and second areas 13 a and 13 b. Forexample, the management area extends in an innermost portion of theoptical disc 13. After the recording of the first and second informationsignals “A” and “B” on the first and second areas 13 a and 13 b in theoptical disc 13 has been completed, address information of the blocks ofthe first and second information signals “A” and “B” on the first andsecond areas 13 a and 13 b is recorded on the management area in theoptical disc 13. Information of the first and second transfer rates Raand Rb may also be recorded on the management area in the optical disc13.

[0223] With reference to FIG. 10, after the degree of occupancy of thefirst area 19 a in the track buffer memory 19 reaches the related fullvalue, the first information signal “A” is transmitted from the memoryarea 19 a to the first area A1 in the optical disc 13 at thepredetermined constant transfer rate Rp and the first information signal“A” is stored into the memory area 19 a from the audio-video encodingand decoding unit 20 at the transfer rate Ra. Thus, during this stage,the degree of occupancy of the memory area 19 a decreases at a ratecorresponding to “Rp−Ra”.

[0224] When the degree of occupancy of the memory area 19 a reaches therelated empty value, the transmission of the first information signal“A” from the memory area 19 a to the first area A1 in the optical disc13 is suspended. Then, the optical head 14 is moved to a positioncorresponding to the second area B1 in the optical disc 13. The seektime Tab related to this movement of the optical head 14 is equal to orshorter than 1.5 seconds. The second information signal “B” is storedinto the second area 19 b of the track buffer memory 19 from theaudio-video encoding and decoding unit 20 at the transfer rate Rb. Evenafter the degree of occupancy of the memory area 19 a reaches therelated empty value, the first information signal “A” continues to bestored into the memory area 19 a from the audio-video encoding anddecoding unit at the transfer rate Ra. Thus, during this stage, thedegree of occupancy of the memory area 19 a increases at a ratecorresponding to “Ra”. The degree of occupancy of the memory area 19 areaches the related full value before the optical head 14 accesses thefirst area A2 in the optical disc 13.

[0225] After the degree of occupancy of the second area 19 b in thetrack buffer memory 19 reaches the related full value, the secondinformation signal “B” is transmitted from the memory area 19 b to thesecond area B1 in the optical disc 13 at the predetermined constanttransfer rate Rp and the second information signal “B” continues to bestored into the memory area 19 b from the audio-video encoding anddecoding unit 20 at the transfer rate Rb. Thus, during this stage, thedegree of occupancy of the memory area 19 b decreases at a ratecorresponding to “Rp−Rb”.

[0226] When the degree of occupancy of the memory area 19 b reaches therelated empty value, the transmission of the second information signal“B” from the memory area 19 b to the second area B1 in the optical disc13 is suspended. Then, the optical head 14 is moved to a positioncorresponding to the first area A2 in the optical disc 13. The seek timeTba related to this movement of the optical head 14 is equal to orshorter than 1.5 seconds. Even after the degree of occupancy of thememory area 19 b reaches the related empty value, the second informationsignal “B” continues to be stored into the memory area 19 b from theaudio-video encoding and decoding unit 20 at the transfer rate Rb. Thus,during this stage, the degree of occupancy of the memory area 19 bincreases at a rate corresponding to “Rb”. The degree of occupancy ofthe memory area 19 b reaches the related full value before the opticalhead 14 accesses the second area B2 in the optical disc 13.

[0227] Preferably, the transfer rate Ra, the transfer rate Rb, the sizeYa of each block of the first information signal “A” on one first area13 a in the optical disc 13, the size Yb of each block of the secondinformation signal “B” on one second area 13 b in the optical disc 13,the seek time Tab related to the movement of the optical head 14 fromthe first area 13 a to the second area 13 b of the optical disc 13, theseek time Tba related to the movement of the optical head 14 from thesecond area 13 b to the first area 13 a of the optical disc 13, and theminimum capacity Ym of the track buffer memory 19 are chosen to satisfythe previously-indicated relations (1)-(18).

[0228] Signal Recording/Playback Mode

[0229]FIG. 11 shows a portion of the apparatus 10A which is operating ina signal recording/playback mode. The amplifier unit 16 and the signalprocessor 18 are omitted from FIG. 11 for a better understanding. Withreference to FIG. 11, the optical head 14 reproduces the firstinformation signal “A” from the first areas 13 a in the optical disc 13.The first information signal “A” is transmitted from the optical head 14to the first area 19 a of the track buffer memory 19 at thepredetermined constant transfer rate Rp. The first information signal“A” is transmitted from the first area 19 a of the track buffer memory19 to the audio-video encoding and decoding unit 20 at the firsttransfer rate Ra. On the other hand, the second information signal “B”is transmitted from the audio-video encoding and decoding unit 20 to thesecond area 19 b in the track buffer memory 19 at the second transferrate Rb. The second information signal “B” is transmitted from thesecond area 19 b in the track buffer memory 19 to the optical head 14 atthe predetermined constant transfer rate Rp. The optical head 14 recordsthe second information signal “B” on the second areas 13 b in theoptical disc 13. The optical head 14 alternately accesses the first andsecond areas 13 a and 13 b of the optical disc 13 on a time sharingbasis so that the playback of the contents of the first informationsignal “A” and the recording of the contents of the second informationsignal “B” can be virtually simultaneously implemented.

[0230] The optical disc 13 is of the rewritable type. The optical disc13 is previously provided with the first areas 13 a for storing thefirst information signal “A”. In addition, the optical disc 13 ispreviously provided with the second areas 13 b for storing the secondinformation signal “B”. The second areas 13 b are separate from thefirst areas 13 a.

[0231] The first areas 13 a in the optical disc 13 are given addressesA1, A2, A3, . . . , respectively (see FIG. 4). Thus, the first areas 13a are also referred to as the first areas A1, A2, A3, . . . . The blocksof the first information signal “A” are recorded on the first areas A1,A2, A3, . . . , respectively. Preferably, the size Ya of the blocks ofthe first information signal “A” is equal to the size of the first areasA1, A2, A3, . . . . The placement of the first areas 13 a is designed tomeet requirements for a seek time. The second areas 13 b in the opticaldisc 13 are given addresses B1, B2, B3, . . . , respectively (see FIG.5). Thus, the second areas 13 b are also referred to as the second areasB1, B2, B3, . . . . The blocks of the second information signal “B” arerecorded on the second areas B1, B2, B3, . . . , respectively.Preferably, the size Yb of the blocks of the second information signal“B” is equal to the size of the second areas B1, B2, B3, . . . . Theplacement of the second areas 13 b is designed to meet the requirementsfor a seek time. First, a block of the information signal “A” isreproduced from the first area Al (the first area 13 a given the addressA1). Second, a block of the information signal “B” is recorded on thesecond area B1 (the second area 13 b given the address B1). The firstarea A1 and the second area B1 are located relative to each other sothat the optical head 14 can move therebetween in a predetermined time(equal to, for example, 1.5 seconds). Therefore, the maximum seek timeduring which the optical head 14 moves between the first area 13 a andthe second area 13 b is equal to the predetermined time (for example,1.5 seconds).

[0232] The system controller 22 operates in accordance with the programstored in its internal ROM. FIG. 12 is a flowchart of a segment of theprogram which relates to the signal recording/playback mode of operationof the apparatus 10A. The program segment in FIG. 12 is started inresponse to a signal-recording/playback start command signal fed fromthe key input unit 23.

[0233] With reference to FIG. 12, a first step S72 of the programsegment decides whether or not the optical head 14 has reached a targetposition on the optical disc 13. Initially, the target positioncorresponds to first one A1 of the first areas 13 a in the optical disc13. When the optical head 14 has not reached the target position yet,the step S72 is repeated. When the optical head 14 has reached thetarget position, the program advances from the step S72 to a step S73.

[0234] The step S73 enables the optical head 14 to reproduce the firstinformation signal “A” from the present first area 13 a in the opticaldisc 13. The step S73 stores the reproduced first information signal “A”into the first area 19 a in the track buffer memory 19 at thepredetermined constant transfer rate Rp.

[0235] A step S74 following the step S73 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related empty value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S74 to thestep S73. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S74 to a step S75.

[0236] The step S75 transfers the first information signal “A” from thefirst area 19 a in the track buffer memory 19 to the audio-videoencoding and decoding unit 20 at the transfer rate Ra.

[0237] A step S76 following the step S75 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related full value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S76 to thestep S75. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S76 to a step S77.

[0238] The step S77 forces the optical head 14 to suspend thereproduction of the first information signal “A” from the present firstarea 13 a in the optical disc 13.

[0239] A step S78 subsequent to the step S77 moves the optical head 14toward a next target position. The next target position corresponds to,for example, first one B1 of the second areas 13 b in the optical disc13. After the step S78, the program advances to a step S79.

[0240] The step S79 decides whether or not the optical head 14 hasreached the target position on the optical disc 13. When the opticalhead 14 has not reached the target position yet, the step S79 isrepeated. When the optical head 14 has reached the target position, theprogram advances from the step S79 to a step S80.

[0241] In this way, the optical head 14 moves from the first area 13 ato the second area 13 b. The seek time Tab related to this movement ofthe optical head 14 is equal to 1.5 seconds or shorter.

[0242] The step S80 stores the second information signal “B”, which isoutputted from the audio-video encoding and decoding unit 20, into thesecond area 19 b in the track buffer memory 19 at the transfer rate Rb.

[0243] A step S81 following the step S80 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related full value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S81 to thestep S80. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S81 to a step S82.

[0244] The step S82 transfers the second information signal “B” from thesecond area 19 b in the track buffer memory 19 to the optical head 14 atthe predetermined constant transfer rate Rp. The step S82 enables theoptical head 14 to record the second information signal “B” on thepresent second area 13 b in the optical disc 13 at the predeterminedconstant transfer rate Rp.

[0245] A step S83 following the step S82 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related empty value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S83 to thestep S82. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S83 to a step S84.

[0246] The step S84 forces the optical head 14 to suspend the recordingof the second information signal “B” on the present second area 13 b inthe optical disc 13.

[0247] A step S85 subsequent to the step S84 moves the optical head 14toward a next target position. The next target position corresponds to,for example, second one A2 of the first areas 13 a in the optical disc13. After the step S85, the program returns to the step S72.

[0248] Thus, the optical head 14 moves from the second area 13 b to thefirst area 13 a. The seek time Tba related to this movement of theoptical head 14 is equal to 1.5 seconds or shorter.

[0249] During the repetitive execution of the program segment in FIG.12, the target position of the optical head 14 is sequentially set intocorrespondence with the first and second areas A1, B1, A2, B2, A3, B3, .. . in the optical disc 13. Therefore, the optical head 14 alternatelyreproduces the first information signal “A” and records the secondinformation signal “B” while accessing the first and second areas 13 aand 13 b of the optical disc 13 in the order as “A1, B1, A2, B2, A3, B3,. . . ”.

[0250] Preferably, the step S77 or the step S84 is followed by a stepwhich decides whether or not both the reproduction of the firstinformation signal “A” from the optical disc 13 and the recording of thesecond information signal “B” thereon are required to be suspended. Inthis case, when both the reproduction of the first information signal“A” from the optical disc 13 and the recording of the second informationsignal “B” thereon are required to be suspended, the optical head 14 iscontrolled to implement the required suspension of reproduction andrecording.

[0251] It is preferable to provide the optical disc 13 with a managementarea separate from the first and second areas 13 a and 13 b. Forexample, the management area extends in an innermost portion of theoptical disc 13. After the recording of the second information signal“B” on the second areas 13 b in the optical disc 13 has been completed,address information of the blocks of the second information signal “B”on the second areas 13 b is recorded on the management area in theoptical disc 13. Information of the second transfer rate Rb may also berecorded on the management area in the optical disc 13.

[0252] With reference to FIG. 13, after the degree of occupancy of thefirst area 19 a in the track buffer memory 19 reaches the related emptyvalue, the first information signal “A” is read out from the memory area19 a at the transfer rate Ra and the first information signal “A” istransmitted from the first area A1 in the optical disc 13 to the memoryarea 19 a at the predetermined constant transfer rate Rp. Thus, duringthis stage, the degree of occupancy of the memory area 19 a increases ata rate corresponding to “Rp−Ra”.

[0253] When the degree of occupancy of the memory area 19 a reaches therelated full value, the transmission of the first information signal “A”from the first area A1 in the optical disc 13 to the memory area 19 a issuspended. Then, the optical head 14 is moved to a positioncorresponding to the second area B1 in the optical disc 13. The seektime Tab related to this movement of the optical head 14 is equal to orshorter than 1.5 seconds. Even after the degree of occupancy of thememory area 19 a reaches the related full value, the first informationsignal “A” continues to be read out from the memory area 19 a at thetransfer rate Ra. Thus, during this stage, the degree of occupancy ofthe memory area 19 a decreases at a rate corresponding to “Ra”. Theread-out of the first information signal “A” from the memory area 19 ais completed before the optical head 14 accesses the first area A2 inthe optical disc 13.

[0254] The second information signal “B” is stored into the second area19 b of the track buffer memory 19 from the audio-video encoding anddecoding unit 20 at the transfer rate Rb. After the degree of occupancyof the second area 19 b in the track buffer memory 19 reaches therelated full value, the second information signal “B” is transmittedfrom the memory area 19 b to the second area B1 in the optical disc 13at the predetermined constant transfer rate Rp and the secondinformation signal “B” continues to be stored into the memory area 19 bfrom the audio-video encoding and decoding unit 20 at the transfer rateRb. Thus, during this stage, the degree of occupancy of the memory area19 b decreases at a rate corresponding to “Rp−Rb”.

[0255] When the degree of occupancy of the memory area 19 b reaches therelated empty value, the transmission of the second information signal“B” from the memory area 19 b to the second area B1 in the optical disc13 is suspended. Then, the optical head 14 is moved to a positioncorresponding to the first area A2 in the optical disc 13. The seek timeTba related to this movement of the optical head 14 is equal to orshorter than 1.5 seconds. Even after the degree of occupancy of thememory area 19 b reaches the related empty value, the second informationsignal “B” continues to be stored into the memory area 19 b from theaudio-video encoding and decoding unit 20 at the transfer rate Rb. Thus,during this stage, the degree of occupancy of the memory area 19 bincreases at a rate corresponding to “Rb”. The degree of occupancy ofthe memory area 19 b reaches the related full value before the opticalhead 14 accesses the second area B2 in the optical disc 13.

[0256] Preferably, the transfer rate Ra, the transfer rate Rb, the sizeYa of each block of the first information signal “A” on one first area13 a in the optical disc 13, the size Yb of each block of the secondinformation signal “B” on one second area 13 b in the optical disc 13,the seek time Tab related to the movement of the optical head 14 fromthe first area 13 a to the second area 13 b of the optical disc 13, theseek time Tba related to the movement of the optical head 14 from thesecond area 13 b to the first area 13 a of the optical disc 13, and theminimum capacity Ym of the track buffer memory 19 are chosen to satisfythe previously-indicated relations (1)-(18).

[0257] In the case where a second information signal “B” is required tobe recorded during the playback of a first information signal “A”, thesecond information signal “B” is inputted into the apparatus 10A and thetransfer rate Rb for the second information signal “B” is set inaccordance with user's selection. At this time, the system controller 22decides the size Yb of blocks of the second information signal “B” onthe basis of the transfer rate Rb, the transfer rate Ra, the seek times,and information of usable areas in the optical disc 13 according to thepreviously-indicated relations (9), (10), and (11). If the sizes of allthe usable areas in the optical disc 13 are smaller than the block sizeYb of the second information signal “B”, the transfer rate Rb is reducedfrom the designated value. Preferably, the user is informed of thereduction in the transfer rate Rb. The recording of the secondinformation signal “B” is implemented while the reduced transfer rate Rbis used.

[0258] It should be noted that the optical disc 13 may he replaced by amagnetic disc or a plurality of magnetic discs. In this case, theoptical-disc drive portion of the apparatus 10A in FIG. 1 is replaced bya magnetic-disc drive portion.

[0259] A first example of the magnetic-disc drive portion includes aplurality of magnetic heads for accessing magnetic discs each having aspiral track. The magnetic heads and the magnetic discs are periodicallychanged and selected to record and reproduce information signals on andfrom the magnetic discs. Each magnetic disc may have a plurality ofconcentric tracks.

Second Embodiment

[0260]FIG. 14 shows an information-signal recording and reproducingapparatus 10B according to a second embodiment of this invention. Theapparatus 10B in FIG. 14 is similar to the apparatus 10A in FIG. 1except for the following design change.

[0261] The apparatus 10B in FIG. 14 includes an optical disc drive 10Dand a solid-state memory unit 10M. The solid-state memory unit 10M isdetachably connected with the optical disc drive 10D. Specifically, thesolid-state memory unit 10M is connected with the optical disc drive 10Dvia a disconnectable connector.

[0262] The optical disc drive 10D includes a spindle motor 11, aturntable 12, an optical head (an optical pickup) 14, a driver 15, anamplifier unit 16, and a servo unit 17. The solid-state memory unit 10Mincludes a signal processor 18, a track buffer memory 19, an audio-videoencoding and decoding unit 20, a memory 21, a system controller 22, akey input unit 23, and an input/output terminal 24.

[0263] When the solid-state memory unit 10M is connected with theoptical disc drive 10D, the apparatus 10B in FIG. 14 operates similarlyto the apparatus 10A in FIG. 1. On the other hand, when the solid-statememory unit 10M is disconnected from the optical disc drive 10D, atleast one of first and second information signals “A” and “B” in thetrack buffer memory 19 or the memory 21 can be played back via thesignal processor 18 and the audio-video encoding and decoding unit 20.

Third Embodiment

[0264]FIG. 15 shows an information-signal communication apparatus 25Aaccording to a third embodiment of this invention. The apparatus 25A inFIG. 15 is similar to the apparatus 10A in FIG. 1 except for designchanges indicated hereinafter.

[0265] The apparatus 25A in FIG. 15 includes a spindle motor 11, aturntable 12, an optical head (an optical pickup) 14, a driver 15, anamplifier unit 16, a servo unit 17, a signal processor 18, a trackbuffer memory 19, and a system controller 22. The devices 11, 12, 14,15, 16, 17, 18, 19, and 22 are connected in a manner similar to that inthe apparatus 10A in FIG. 1. The apparatus 25A in FIG. 15 furtherincludes an ATAPI (AT attachment packet interface) unit 26, that is, aninterface 26 of an ATAPI type. The interface 26 is connected to thesignal processor 18.

[0266] A host computer or an external apparatus 27 can be connected withthe apparatus 25A in FIG. 15 via the interface 26. The externalapparatus 27 includes an audio-video encoding and decoding unit 20, amemory 21, and a host computer unit 27A. The memory 21 and the hostcomputer unit 27A are connected to the audio-video encoding and decodingunit 20. The audio-video encoding and decoding unit 20 can be connectedwith the signal processor 18 in the apparatus 25A via the interface 26.

[0267] In more detail, the ATAPI unit 26 includes an interface block.The audio-video encoding and decoding unit 20 includes an interfaceblock which can be connected with the interface block in the ATAPI unit26. The apparatus 27 can control the apparatus 25A while using controlsignals in the Mt. Fuji command system.

[0268] In the case where first and second information signals “A” and“B” are required to be recorded, the host computer unit 27A in theapparatus 27 transmits information of transfer rates Ra and Rb for thefirst and second information signals “A” and “B” (transfer-raterepresenting flags) to the apparatus 25A via the audio-video encodingand decoding unit 20 and the interface 26. The audio-video encoding anddecoding unit 20 in the apparatus 27 transmits the first and secondinformation signals “A” and “B to the signal processor 18 in theapparatus 25A via the interface 26. In addition, the host computer unit27A in the apparatus 27 transmits a recording start command signal and arecording start address signal to the apparatus 25A via the audio-videoencoding and decoding unit and the interface 26.

[0269] In the case where first and second information signals “A” and“B” are required to be reproduced from an optical disc 13, the hostcomputer unit 27A in the apparatus 27 transmits a playback start commandsignal and a disc address signal to the apparatus 25A via theaudio-video encoding and decoding unit 20 and the interface 26. Theapparatus 25A reproduces a signal (for example, control data ormanagement information) from a portion of the optical disc 13 whoseposition is designated by the disc address signal. The host computerunit 27A in the apparatus 27 receives the reproduced signal from theapparatus 25A via the interface 26 and the audio-video encoding anddecoding unit 20, and calculates transfer rates Ra and Rb on the basisof the reproduced signal. The host computer unit 27A in the apparatus 27transmits information of the calculated transfer rates Ra and Rb(transfer-rate representing flags) to the apparatus 25A via theaudio-video encoding and decoding unit 20 and the interface 26. Then,the apparatus 25A reproduces the first and second information signals“A” and “B” while using the transfer rates Ra and Rb.

[0270] The interface 26 may be of an IEEE1394 type rather than the ATAPItype. The interface 26 may be of a wireless type using a radio signal ora light signal.

Fourth Embodiment

[0271]FIG. 16 shows an information-signal communication apparatus 25Baccording to a fourth embodiment of this invention. The apparatus 25B inFIG. 16 is similar to the apparatus 25A in FIG. 15 except for thefollowing design change.

[0272] The apparatus 25B in FIG. 16 includes an optical disc drive 25Dand a solid-state memory unit 25M. The solid-state memory unit 25M isdetachably connected with the optical disc drive 25D and an interface26. Specifically, the solid-state memory unit 25M is connected with theoptical disc drive 25D and the interface 26 via disconnectableconnectors.

[0273] The optical disc drive 25D includes a spindle motor 11, aturntable 12, an optical head (an optical pickup) 14, a driver 15, anamplifier unit 16, and a servo unit 17. The solid-state memory unit 25Mincludes a signal processor 18, a track buffer memory 19, and a systemcontroller 22. The signal processor 18 can be connected with theinterface 26.

[0274] A host computer or an external apparatus 27 can be connected withthe signal processor 18 in the solid-state memory unit 25M via theinterface 26. The external apparatus 27 includes an audio-video encodingand decoding unit 20, a memory 21, and a host computer unit 27A. Thememory 21 and the host computer unit 27A are connected to theaudio-video encoding and decoding unit 20. The audio-video encoding anddecoding unit 20 can be connected with the signal processor 18 in theapparatus 25A via the interface 26.

[0275] When the solid-state memory unit 25M is connected with theoptical disc drive 25D and the interface 26, the apparatus 25B in FIG.16 operates similarly to the apparatus 25A in FIG. 15. On the otherhand, when the solid-state memory unit 25M is disconnected from theoptical disc drive 25D and the interface 26, at least one of first andsecond information signals “A” and “B” in the track buffer memory 19 canbe played back via the signal processor 18.

Fifth Embodiment

[0276]FIG. 17 shows an information-signal recording and reproducingapparatus 110 according to a fifth embodiment of this invention. Theapparatus 110 operates on an information-signal recording mediumincluding an optical disc. Examples of the optical disc are a DVD-ROM, aDVD-RAM, a DVD-RW, and a DVD+RW. Alternatively, the informationrecording medium may include a magnetic disc such as a hard disc or afloppy disc. The information recording medium may include asemiconductor memory.

[0277] As shown in FIG. 17, the apparatus 110 includes a spindle motor111, and a turntable 112 connected to the shaft of the spindle motor111. An optical disc (an information-signal recording medium) 113 can beplaced on the turntable 112. The apparatus 110 further includes anoptical head (an optical pickup) 114, a driver 115, an amplifier unit116, a servo unit 117, a signal processor 118, a track buffer memory119, an audio-video encoding and decoding unit 120, a memory 121, asystem controller 122, a key input unit 123, an NTSC encoder 124, adisplay 125, and input terminals 126(1), 126(2), . . . , and 126(n).Here, “n” denotes a predetermined natural number equal to or greaterthan 2. In addition, the apparatus 110 includes a satellite digitalbroadcasting reception antenna 141, a satellite digital broadcastingdecoder 142, a switch 143, a stream converter 144, and a terminal 145.

[0278] When the optical disc 113 is placed on the turntable 112, thespindle motor 111 rotates the turntable 112 and the optical disc 113. Inthe case where the optical disc 113 is of a rewritable type, the opticalhead 114 writes and reads information thereon and therefrom. In the casewhere the optical disc 113 is designed exclusively for playback, theoptical head 114 only reads information therefrom. The spindle motor 111is connected to the driver 115 and the servo unit 117. The optical head114 is connected to the amplifier unit 116 and the driver 115. Theamplifier unit 116 is connected to the servo unit 117 and the signalprocessor 118. The driver 115 is connected to the servo unit 117. Thesignal processor 118 is connected to the track buffer memory 119 and theaudio-video encoding and decoding unit 120. The audio-video encoding anddecoding unit 120 is connected to the memory 121 and the input terminals126(1)-126(n). The system controller 122 is connected to the amplifierunit 116, the servo unit 117, the signal processor 118, the audio-videoencoding and decoding unit 120, and the key input unit 123.

[0279] The NTSC encoder 124 is connected to the audio-video encoding anddecoding unit 120. The display 125 is connected to the NTSC encoder 124.The satellite digital broadcasting reception antenna 141 is connected tothe satellite digital broadcasting decoder 142. The satellite digitalbroadcasting decoder 142 is connected to the switch 143. The switch 143is connected to the stream converter 144. The switch 143 is connected tothe Internet via the terminal 145. The stream converter 144 is connectedto the signal processor 118. The satellite digital broadcasting decoder142, the switch 143, the stream converter 144, and the system controller122 are connected to each other.

[0280] The spindle motor 111 is driven and controlled by the driver 115.The spindle motor 111 rotates the turntable 112 and the optical disc113. The spindle motor 111 is provided with an FG generator and arotational position sensor (an angular position sensor). The rotationalposition sensor includes, for example, a Hall element. The FG generatoroutputs an FG signal (a rotational speed signal). The Hall elementoutputs a rotational position signal. The FG signal and the rotationalposition signal are fed back to the driver 115 and the servo unit 117 asrotation servo signals.

[0281] The optical head 114 faces the optical disc 113 placed on theturntable 112. A feed motor (not shown) moves the optical head 114radially with respect to the optical disc 113. The feed motor is drivenby the driver 115. The optical head 114 includes a semiconductor laser,a collimator lens, and an objective lens. The semiconductor laser actsas a source for emitting a light beam (a laser beam). The emitted laserbeam is focused into a laser spot on the optical disc 113 by thecollimator lens and the objective lens. The optical head 114 includes a2-axis actuator for driving the objective lens to implement focusing andtracking of the laser spot with respect to the optical disc 113. Thesemiconductor laser is driven by a laser drive circuit in the opticalhead 114. In the case where an information signal such as an audiosignal or an audio-video signal is recorded, the information signal issubjected to waveform correction by a waveform correction circuit in theamplifier unit 116 before being fed to the laser drive circuit. The2-axis actuator is driven by the driver 115.

[0282] The key input unit 123 includes a plurality of keys which can beoperated by a user. The key input unit 123 generates command signals inaccordance with its operation by the user. The command signals aretransmitted from the key input unit 123 to the system controller 122.The command signals include a command signal for starting a recordingmode of operation of the apparatus 110, and a command signal forstarting a playback mode of operation of the apparatus 110. The keyinput unit 123 generates control data in accordance with its operationby the user. The control data are transmitted from the key input unit123 to the system controller 122.

[0283] The system controller 122 includes, for example, a microcomputeror a similar device which operates in accordance with a program storedin its internal ROM. The system controller 122 controls the amplifierunit 116, the servo unit 117, the signal processor 118, and theaudio-video encoding and decoding unit 120 in response to the commandsignals fed from the key input unit 123.

[0284] Control data can be fed to the system controller 122 via an inputterminal (not shown). The control data fed to the system controller 122via the input terminal, and the control data fed to the systemcontroller 122 from the key input unit 123 include a signal foradjusting the resolution of pictures represented by contents informationto be recorded, a signal for separating quickly-moving scenes such ascar racing scenes represented by contents information, and a signal forgiving priority to a recording time. The system controller 122 changesan actual recording time in accordance with the control data. The systemcontroller 122 enables the setting of the actual recording time to beselected by the user.

[0285] When the apparatus 110 is required to start to operate in theplayback mode, the key input unit 123 is actuated to generate theplayback start command signal. The playback start command signal istransmitted from the key input unit 123 to the system controller 122.The system controller 122 controls the amplifier unit 116 and the servounit 117 in response to the playback start command signal, therebystarting the playback mode of operation of the apparatus 110. Thecontrol of the servo unit 117 includes steps of controlling the driver115. Firstly, the system controller 122 starts rotation of the opticaldisc 113 and application of a laser spot thereon through the control ofthe driver 115. The optical head 114 is controlled by the driver 115,thereby reading out address information from the optical disc 113. Forexample, the address information is contained in management informationstored in a management area of the optical disc 113. The read-outaddress information is transmitted from the optical head 114 to thesystem controller 122 via the amplifier unit 116. The system controller122 finds or decides a target sector (a target track portion) to beplayed back by referring to the address information. The systemcontroller 122 controls the optical head 114 via the servo unit 117, thedriver 115, and the feed motor, thereby moving the optical head 114radially with respect to the optical disc 113 and hence moving the laserspot to the target sector on the optical disc 113. When the movement ofthe laser spot to the target sector is completed, the system controller122 operates to start the reproduction of a signal from the targetsector on the optical disc 113. In this way, the playback mode ofoperation of the apparatus 110 is started. During the playback mode ofoperation of the apparatus 110, the target sector is repetitivelychanged from one to another.

[0286] During the playback mode of operation of the apparatus 110, theoptical head 114 scans the optical disc 113 and generates an RF signalcontaining information read out therefrom. A unit of generation of theRF signal corresponds to one correction block of the informationrecorded on the optical disc 113. The optical head 114 outputs the RFsignal to the amplifier unit 116. The amplifier unit 116 enlarges the RFsignal. In addition, the amplifier unit 116 generates a main reproducedsignal, and tracking and focusing servo signals (tracking error andfocusing error signals) from the enlarged RF signal. The amplifier unit116 includes an equalizer for optimizing the frequency aspect of themain reproduced signal. Also, the amplifier unit 116 includes a PLL(phase locked loop) circuit for extracting a bit clock signal from theequalized main reproduced signal, and for generating a speed servosignal from the equalized main reproduced signal. Furthermore, theamplifier unit 116 includes a jitter generator for comparing the timebases of the bit clock signal and the equalized main reproduced signal,and for detecting jitter components from the results of the time-basecomparison. A signal of the detected jitter components is transmittedfrom the amplifier unit 116 to the system controller 122. The trackingand focusing servo signals and the speed servo signal are transmittedfrom the amplifier unit 116 to the servo unit 117. The equalized mainreproduced signal is transmitted from the amplifier unit 116 to thesignal processor 118.

[0287] The servo unit 117 receives the speed servo signal and thetracking and focusing servo signals from the amplifier unit 116. Theservo unit 117 receives the rotation servo signals from the spindlemotor 111. In response to these servo signals, the servo unit 117implements corresponding servo control processes.

[0288] Specifically, the servo unit 117 generates a rotation controlsignal on the basis of the speed servo signal and the rotation servosignals. The rotation control signal is transmitted from the servo unit117 to the spindle motor 111 via the driver 115. The spindle motor 111rotates at a speed depending on the rotation control signal. Therotation control signal is designed to rotate the optical disc 113 at agiven constant linear velocity.

[0289] In addition, the servo unit 117 generates servo control signalson the basis of the focusing and tracking servo signals. The servocontrol signals are transmitted from the servo unit 117 to the 2-axisactuator in the optical head 114 via the driver 115. The 2-axis actuatorcontrols the laser spot on the optical disc 113 in response to the servocontrol signals, and thereby implements focusing and tracking of thelaser spot with respect to the optical disc 113.

[0290] During the playback mode of operation of the apparatus 110, thesignal processor 118 receives the main reproduced signal from theamplifier unit 116. The signal processor 118 is controlled by the systemcontroller 122, thereby converting the main reproduced signal into acorresponding reproduced digital signal. The signal processor 118detects a sync signal from the reproduced digital signal. The signalprocessor 118 decodes an EFM+ signal (an 8-16 modulation signal) of thereproduced digital signal into NRZ data, that is, non-return-to-zerodata. The signal processor 118 subjects the NRZ data to an errorcorrection process for every correction block, thereby generating asector address signal and a plurality of information signals (“n”information signals). Here, “n” denotes a predetermined natural numberequal to or greater than 2. The “n” information signals include a firstinformation signal, a second information signal, . . . , and an n-thinformation signal. The sector address signal represents the address ofa currently-accessed sector on the optical disc 113. The sync signal andthe sector address signal are fed from the signal processor 118 to thesystem controller 122. It should be noted that the “n” informationsignals generated by the signal processor 118 correspond to informationsignals resulting from compression at variable transfer rates (variabletransmission rates) during a recording mode of operation.

[0291] During the playback mode of operation of the apparatus 110, thesignal processor 118 temporarily stores the “n” information signals inthe track buffer memory 119. Thus, the signal processor 118 writes the“n” information signals into the track buffer memory 119, and reads the“n” information signals therefrom. Writing and reading the “n”information signals into and from the track buffer memory 119 arecontrolled to absorb a time-domain change in the transfer rates of the“n” information signals. The track buffer memory 119 includes, forexample, a D-RAM having a capacity of 64 Mbytes. The signal processor118 outputs the read-out signal (the “n” information signals read outfrom the track buffer memory 119) to the audio-video encoding anddecoding unit 120.

[0292] In the case where the “n” information signals fed from the trackbuffer memory 119 via the signal processor 118 are compressed MPEG2 datain which audio data and video data are multiplexed, the audio-videoencoding and decoding unit 120 separates the “n” information signalsinto compressed audio data and compressed video data. The audio-videoencoding and decoding unit 120 expands and decodes the compressed audiodata into non-compressed audio data. In addition, the audio-videencoding and decoding unit 120 expands and decodes the compressed videodata into non-compressed video data. During the expansively decodingprocess, the audio-video encoding and decoding unit 120 temporarilystores signals and data in the memory 121. The memory 121 includes, forexample, a D-RAM having a capacity of 64 Mbytes. The audio-videoencoding and decoding unit 120 converts the non-compressed audio datainto a corresponding analog audio signal through digital-to-analogconversion. Also, the audio-video encoding and decoding unit 120converts the non-compressed video data into a corresponding analog videosignal through digital-to-analog conversion. It should be noted that theconversion of the non-compressed audio and video data into the analogaudio and video signals may be implemented by digital-to-analogconverters provided externally of the audio-video encoding and decodingunit 120. The audio-video encoding and decoding unit 120 outputs theanalog audio signal and the analog video signal to the NTSC converter124. The analog audio signal passes through the NTSC converter 124before being applied to loudspeakers provided in the body of the display125. The NTSC converter 124 changes the analog video signal into acorresponding NTSC video signal. The NTSC converter 124 outputs the NTSCvideo signal to the display 125.

[0293] The data rate of the expansively decoding process by theaudio-video encoding and decoding unit 120, that is, the data transferrate (the data transmission rate) in the expansively decoding process,is equalized to an expansion data rate which is set in accordance withthe type of the related recording mode of operation of the apparatus110. Specifically, the audio-video encoding and decoding unit 120 canimplement the expansively decoding process at a expansion data ratewhich can be changed among plural different expansion data rates. Theaudio-video encoding and decoding unit 120 selects one from among theplural different expansion data rates as a desired expansion data ratein accordance with the type of the related recording mode of operationof the apparatus 110. The audio-video encoding and decoding unit 120executes the expansively encoding process at the desired expansion datarate. Information of the type of the recording mode of operation of theapparatus 110 is recorded on the optical disc 113 as control data whichmay be contained in the management information. During the playback ofthe optical disc 113, the control data are read out therefrom beforebeing transmitted to the system controller 122. The system controller122 sets the expansion data rate in the audio-video encoding anddecoding unit 120 in accordance with the control data.

[0294] When the apparatus 110 is required to start to operate in therecording mode, the key input unit 123 is actuated to generate therecording start command signal. The recording start-command signal istransmitted from the key input unit 123 to the system controller 122.The system controller 122 controls the amplifier unit 116 and the servounit 117 in response to the recording start command signal, therebystarting the recording mode of operation of the apparatus 110. Thecontrol of the servo unit 117 includes steps of controlling the driver115. Firstly, the system controller 122 starts rotation of the opticaldisc 113 and application of a laser spot thereon through the control ofthe driver 115. The optical head 114 is controlled by the driver 115,thereby reading out address information from the optical disc 113. Forexample, the address information is contained in management informationstored in the management area of the optical disc 113. The read-outaddress information is transmitted from the optical head 114 to thesystem controller 122 via the amplifier unit 116. The system controller122 finds or decides a target sector (a target track portion), on whicha signal is to be recorded, by referring to the address information. Thesystem controller 122 controls the optical head 114 via the servo unit117, the driver 115, and the feed motor, thereby moving the optical head114 radially with respect to the optical disc 113 and hence moving thelaser spot to the target sector on the optical disc 113. During therecording mode of operation of the apparatus 110, the target sector isrepetitively changed from one to another.

[0295] During the recording mode of operation of the apparatus 110, “n”analog information signals to be recorded are fed to the audio-videoencoding and decoding unit 120 via the input terminals 126(1)-126(n)respectively. The audio-video encoding and decoding unit 120 convertsthe “n” analog information signals into corresponding “n” digitalinformation signals through analog-to-digital conversion. It should benoted that the conversion of the “n” analog information signals into the“n” digital information signals may be implemented by analog-to-digitalconverters provided externally of the audio-video encoding and decodingunit 120. The audio-video encoding and decoding unit 120 compressivelyencodes the “n” digital information signals into “n” MPEG2 informationsignals at rates depending on the type of the recording mode. Theaudio-video encoding and decoding unit 120 outputs the “n” MPEG2information signals to the signal processor 118 on a time sharing basis.The data rates of the compressively encoding process by the audio-videoencoding and decoding unit 120, that is, the data transfer rates (thedata transmission rates) in the compressively encoding process, areequalized to compression data rates which are selected from among pluraldifferent rates in accordance with the type of the recording mode ofoperation of the apparatus 110. During the compressively encodingprocess, the audio-video encoding and decoding unit 120 temporarilystores data in the memory 121.

[0296] It should be noted that the “n” MPEG2 information signals may bereplaced by still-picture data or computer data such as program filedata. In this case, the still-picture data or the computer data aretransmitted to the system controller 122 via an interface (not shown).The system controller 122 transfers the still-picture data or thecomputer data to the signal processor 118.

[0297] Alternatively, the “n” MPEG2 information signals may be replacedby “n” compression-resultant information signals composing a transportstream signal. In this case, radio signals containing “n”compression-resultant information signals are received by the satellitedigital broadcasting reception antenna 141, and the received radiosignals are fed from the antenna 141 to the satellite digitalbroadcasting decoder 142. The satellite digital broadcasting decoder 142subjects the received radio signals to QPSK demodulation, an errorcorrection process, and a stream generating process, thereby convertingthe received radio signals into a transport stream signal composed of188-byte segments representative of the “n” compression-resultantinformation signals. The satellite digital broadcasting decoder 142outputs the transport stream signal to the switch 143. In addition, “n”compression-resultant information signals composing a transport streamsignal are fed from the Internet to the switch 143 via the terminal 145.The switch 143 selects one of a set of the “n” compression-resultantinformation signals (the transport stream signal) fed from the satellitedigital broadcasting decoder 142 and a set of the “n”compression-resultant information signals (the transport stream signal)fed via the terminal 145, and outputs the selected signal set to thestream converter 144. The selection by the switch 143 responds to aswitch control signal fed from the system controller 122. The switchcontrol signal is generated in response to, for example, user'soperation of the key input unit 123. The stream converter 144 changesthe output signals of the switch 143 into a program stream composed of2048-byte segments representative of the “n” selectedcompression-resultant information signals. The stream converter 144 mayencrypt the “n” selected compression-resultant information signals inaccordance with key information recorded on the optical disc 113. Thestream converter 144 outputs the program stream to the signal processor118.

[0298] During the recording mode of operation of the apparatus 110, thesignal processor 118 adds error correction code signals (ECC signals) tothe “n” MPEG2 information signals, the still-picture data, the computerdata, or the “n” compression-resultant information signals. The signalprocessor 118 subjects the ECC-added data (the ECC-added signals) to NRZand EFM+ encoding processes. The signal processor 118 adds a sync signalto the encoding-resultant data to form sync-added data. The sync signalis fed from the system controller 122. The sync-added data aretemporarily stored in the track buffer memory 119. The sync-added dataare read out from the track buffer memory 119 at a data ratecorresponding to a data rate of signal recording on the optical disc113. The signal processor 118 subjects the read-out data to givenmodulation for record. The signal processor 118 outputs themodulation-resultant signal to the amplifier unit 116. The amplifierunit 116 corrects the waveform of the output signal of the signalprocessor 118. The amplifier unit 116 outputs thewaveform-correction-resultant signal to the laser drive circuit in theoptical head 114. The optical head 114 records the output signal of theamplifier unit 116 on the target sector (the target track portion) onthe optical disc 113.

[0299] The amplifier unit 116 informs the system controller 122 ofdetected jitter components. The system controller 122 subjects thedetected jitter components to analog-to-digital conversion to generate ameasured jitter value. During the recording mode of operation of theapparatus 110, the system controller 122 adjusts the degree orcharacteristic of the waveform correction by the amplifier unit 116 inresponse to the measured jitter value and an asymmetry value.

[0300] Operation of the apparatus 110 can be changed among variousmodes. During a first mode of operation, the apparatus 110 reproduces anaudio signal or an audio-video signal from the optical disc 113. Duringa second mode of operation, the apparatus 110 records an audio signal oran audio-video signal on the optical disc 113. During a third mode ofoperation, the apparatus 110 records an audio signal or an audio-videosignal on one area of the optical disc 113 while reproducing an audiosignal or an audio-video signal from another area of the optical disc113. During a fourth mode of operation, the apparatus 110 reproduces anaudio signal or an audio-video signal from one area of the optical disc113 while recording an audio signal or an audio-video signal on anotherarea of the optical disc 113. During a fifth mode of operation, theapparatus 110 reproduces an audio signal or an audio-video signal fromone area of the optical disc 113 while reproducing an audio signal or anaudio-video signal from another area of the optical disc 113. During asixth mode of operation, the apparatus 110 records an audio signal or anaudio-video signal on one area of the optical disc 113 while recordingan audio signal or an audio-video signal on another area of the opticaldisc 113. These various modes of operation of the apparatus 110 meetuser's requests for the implementation of an after-recording process anda different-channel-program recording process.

[0301] The apparatus 110 can record “n” information signals on differentareas of the optical disc 113, respectively, on a time sharing basis.The “n” information signals are “n” audio-video information signalsrespectively. Alternatively, the “n” information signals may be “n”audio information signals respectively. The apparatus 110 can recordonly one of the “n” information signals on the optical disc 113.

[0302] The apparatus 110 can reproduce “n” information signals fromdifferent areas of the optical disc 113, respectively, on a time sharingbasis. The “n” information signals are “n” audio-video informationsignals respectively. Alternatively, the “n” information signals may be“n” audio information signals respectively. The apparatus 110 canreproduce only one of the “n” information signals from the optical disc113.

[0303]FIG. 18 shows a portion of the apparatus 110. The amplifier unit116 and the signal processor 118 are omitted from FIG. 18 for a betterunderstanding. As shown in FIG. 18, the optical disc 113 has first,second, . . . , and n-th areas 113(1), 113(2), . . . , and 113(n)assigned to first, second, . . . , and n-th information signalsrespectively. The first, second, . . . , and n-th areas 113(1), 113(2),. . . , and 113(n) are separate from each other. Each of the first,second, . . . , and n-th areas 113(1), 113(2), . . . , and 113(n) isdivided into separate equal-size sub-areas. The first information signalis divided into blocks each having a predetermined size (a predeterminedtotal number of bits) Y1. The sub-areas of the first area 113(1) areallocated to the blocks of the first information signal, respectively.The second information signal is divided into blocks each having apredetermined size (a predetermined total number of bits) Y2. Thesub-areas of the second area 113(2) are allocated to the blocks of thesecond information signal, respectively. The third and later informationsignals, and the third and later areas 113(3) . . . are similarlydesigned. The n-th information signal is divided into blocks each havinga predetermined size (a predetermined total number of bits) Yn. Thesub-areas of the n-th area 113(n) are allocated to the blocks of then-th information signal, respectively. Each of the predetermined sizesY1, Y2, . . . , and Yn is a unit (a unit capacity) for continuousreproduction (or continuous recording) of information, or a unit (a unitcapacity) for reproduction (or recording) of continuous information. Thefirst, second, . . . , and n-th information signals are related orunrelated to each other. Each of the first, second, . . . , and n-thinformation signals represents audio data, video data, audio-video data,or computer data.

[0304] As shown in FIG. 19, the sub-areas in the first area 113(1) ofthe optical disc 113 are given addresses A1, A2, A3, . . . ,respectively. Thus, the sub-areas in the first area 113(1) are alsoreferred to as the sub-areas A1, A2, A3, . . . . The blocks of the firstinformation signal are assigned to the sub-areas A1, A2, A3, . . . ,respectively. Preferably, the size Y1 of the blocks of the firstinformation signal is equal to the size of the sub-areas A1, A2, A3, . .. . The placement of the sub-ares in the first area 113(1) is designedto meet requirements for a seek time. As shown in FIG. 20, the sub-areasin the second area 113(2) of the optical disc 113 are given addressesB1, B2, B3, . . . , respectively. Thus, the sub-areas in the second area113(2) are also referred to as the sub-areas B1, B2, B3, . . . . Theblocks of the second information signal are assigned to the sub-areasB1, B2, B3, . . . , respectively. Preferably, the size Y2 of the blocksof the second information signal is equal to the size of the sub-areasB1, B2, B3, . . . . The placement of the sub-areas in the second area113(2) is designed to meet requirements for a seek time. The sub-areasin each of the third and later areas 113(3) . . . of the optical disc113, and the blocks of each of the third and later information signalsare similarly designed. As shown in FIG. 21, the sub-areas in the n-tharea 113(n) of the optical disc 113 are given addresses N1, N2, N3, . .. , respectively. Thus, the sub-areas in the n-th area 113(n) are alsoreferred to as the sub-areas N1, N2, N3, . . . . The blocks of the n-thinformation signal are assigned to the sub-areas N1, N2, N3, . . . ,respectively. Preferably, the size Yn of the blocks of the n-thinformation signal is equal to the size of the sub-areas N1, N2, N3, . .. . The placement of the sub-areas in the n-th area 113(n) is designedto meet requirements for a seek time.

[0305] During an example of the recording or playback mode of operationof the apparatus 110, the optical head 114 accesses the sub-area A1 inthe first area 113(1) of the optical disc 113 before accessing thesub-area B 1 in the second area 113(2) of the optical disc 113. Thesub-area A1 and the sub-area B1 are located relative to each other sothat the optical head 114 can move therebetween in a predetermined time(equal to, for example, 1.5 seconds). Therefore, the maximum seek timeduring which the optical head 114 moves between the sub-area A1 and thesub-area B1 is equal to the predetermined time (for example, 1.5seconds). Similarly, the maximum seek time during which the optical head114 moves from one sub-area to a next sub-area is equal to thepredetermined time (for example, 1.5 seconds).

[0306] As shown in FIG. 18, an innermost portion of the optical disc 113has a management area 113 x. As shown in FIG. 22, the management area113 x is divided into separate sub-areas which are given addresses X1,X2, X3, . . . , respectively. Thus, the sub-areas in the management area113 x are also referred to as the sub-areas X1, X2, X3, . . . . In thecase where the first, second, . . . , and n-th areas 113(1), 113(2), . .. , and 113(n) of the optical disc 113 store the first, second, and n-thinformation signals respectively, the management area 113 x is loadedwith copyright information, title information, signals representative ofthe transfer rates R1, R2, . . . , and Rn, and signals representative ofstart addresses and end addresses for the first, second, and n-thinformation signals. In the case where the first, second, . . . , andn-th areas 113(1), 113(2), . . . , and 113(n) of the optical disc 113are unoccupied and do not store the first, second, and n-th informationsignals respectively, the management area 113 x is loaded with signalsrepresentative of the start addresses and the end addresses of theunoccupied regions (the unoccupied areas).

[0307] The track buffer memory 119 has first, second, . . . , and n-thareas 119(1), 119(2), . . . , and 119(n) which are assigned to thefirst, second, . . . , and n-th information signals respectively.

[0308] With reference to FIG. 18, the optical head 114 transfers thefirst, second, . . . , and n-th information signals between the opticaldisc 113 and the track buffer memory 119 on a time sharing basis and ata predetermined constant transfer rate Rp. The predetermined constanttransfer rate Rp is equal to, for example, Mbps.

[0309] The first information signal is transferred between the trackbuffer memory 119 and the audio-video encoding and decoding unit 120 ata transfer rate R1 selected from among predetermined values. All thepredetermined values are lower than the predetermined constant transferrate Rp related to the optical head 114. The second information signalis transferred between the track buffer memory 119 and the audio-videoencoding and decoding unit 120 at a transfer rate R2 changeable amongthe predetermined values. Similarly, the third and later informationsignals are transferred between the track buffer memory 119 and theaudio-video encoding and decoding unit 120. The n-th information signalis transferred between the track buffer memory 119 and the audio-videoencoding and decoding unit 120 at a transfer rate Rn changeable amongthe predetermined values.

[0310] As will be mentioned later, the apparatus 110 can substantiallycontinuously and simultaneously record or reproduce the contents of atleast two of the “n” information signals.

[0311] In more detail, each of the transfer rates R1, R2, . . . , and Rnis selected from among a value of 8 Mbps which corresponds to arecording time of 2 hours and a high picture quality, a value of 4 Mbpswhich corresponds to a recording time of 4 hours and a slightly highpicture quality, and a value of 2 Mbps which corresponds to a recordingtime of 8 hours and a normal picture quality. Ones of these values canbe designated as desired values of the transfer rates R1, R2, . . . ,and Rn according to user's operation of the key input unit 123 (see FIG.17). A value of 17 Mbps may be added to the candidate values. During therecording of the “n” information signals on the optical disc 113, thetransfer rates R1, R2, . . . , and Rn are set to the desired valuesdesignated by user's operation of the key input unit 123. During thereproduction of the “n” information signals from the optical disc 113,information of recording compression rates is derived from control datain the “n” information signals, and the transfer rates R1, R2, . . . ,and Rn are set in response to the recording compression rates.Alternatively, during the reproduction of the “n” information signalsfrom the optical disc 113, control data (management information)representative of transfer rates R1, R2, . . . , and Rn are reproducedfrom the optical disc 113, and the actual transfer rates R1, R2, . . . ,and Rn are set in accordance with the reproduced control data.

[0312] The system controller 122 (see FIG. 17) controls the track buffermemory 119 via the signal processor 118 (see FIG. 17). The systemcontroller 122 virtually divides or partitions the track buffer memory119 into the first, second, . . . , and n-th areas 119(1), 119(2), . . ., and 119(n). Specifically, the system controller 122 sets the first,second, . . . , and n-th areas 119(1), 119(2), . . . , and 119(n) in thetrack buffer memory 119 in response to the values of the transfer ratesR1, R2, . . . , and Rn. The ratio in capacity among the first, second, .. . , and n-th areas 119(1), 119(2), . . . and 119(n) depends on theratio among the transfer rates R1, R2, . . . , and Rn. Regarding thefirst area 119(1) in the track buffer memory 119, the system controller122 sets an empty value and a full value in response to the value of thetransfer rate R1. The empty value corresponds to a slightly occupiedstate or a substantially empty state of the first area 119(1). The fullvalue corresponds to a fully occupied state of the first area 119(1).Regarding the second area 119(2) in the track buffer memory 119, thesystem controller 122 sets an empty value and a full value in responseto the value of the transfer rate R2. The empty value corresponds to aslightly occupied state or a substantially empty state of the secondarea 119(2). The full value corresponds to a fully occupied state of thesecond area 119(2). Similarly, regarding each of the third and laterareas 119(3) . . . . in the track buffer memory 119, the systemcontroller 122 sets an empty value and a full value in response to thevalue of the related transfer rate. Regarding the n-th area 119(n) inthe track buffer memory 119, the system controller 122 sets an emptyvalue and a full value in response to the value of the transfer rate Rn.The empty value corresponds to a slightly occupied state or asubstantially empty state of the n-th area 119(n). The full valuecorresponds to a fully occupied state of the n-th area 119(n). Thesystem controller 122 always monitors the degree of occupancy of each ofthe first, second, . . . , and n-th areas 119(1), 119(2), . . . , and119(n) which varies between the related empty value and the related fullvalue under normal conditions.

[0313] Alternatively, the division of the track buffer memory 119 intothe first, second, . . . , and n-th areas 119(1), 119(2), . . . , and119(n) may be responsive to the type of the mode of operation of theapparatus 110. For example, in the case of the operation mode duringwhich the apparatus 110 reproduces first one of the “n” informationsignals and records second one of the “n” information signals, greaterone of the first, second, . . . , and n-th areas 119(1), 119(2), . . . ,and 119(n) is assigned to the information signal to be recorded whilesmaller one is assigned to the reproduced information signal. Thisdesign reliably prevents the occurrence of an interruption of thecontinuously recording of the contents of the information signal. Thesystem controller 122 implements the division of the track buffer memory119 into the first, second, . . . , and n-th areas 119(1), 119(2), . . ., and 119(n) when receiving a recording start command signal or aplayback start command signal. Preferably, the system controller 122implements the division of the track buffer memory 119 after confirmingthe absence of data from the track buffer memory 119 which are beingreproduced or recorded.

[0314] A first mode of operation of the apparatus 110 is executed in thecase where the optical disc 113 is designed exclusively for playback.During the first mode of operation, the optical head 114 reproduces thefirst, second, . . . , and n-th information signals from the first,second, . . . , and n-th areas 113(1), 113(2), . . . , and 113(n) of theoptical disc 113 on a time sharing basis. The first, second, . . . , andn-th information signals are transmitted from the optical head 114 tothe track buffer memory 119. The first, second, . . . , and n-thinformation signals are stored into the first, second, . . . , and n-thareas 119(1), 119(2), . . . , and 119(n) of the track buffer memory 119at the predetermined constant transfer rate Rp.

[0315] The first, second, . . . , and n-th information signals aretransmitted from the first, second, . . . , and n-th areas 119(1),119(2), . . . , and 119(n) of the track buffer memory 119 at therespective transfer rates R1, R2, . . . , and Rn lower than thepredetermined constant transfer rate Rp.

[0316] A second mode of operation of the apparatus 110 is executed inthe case where the optical disc 113 is of the rewritable type. Duringthe second mode of operation, the first, second, . . . , and n-thinformation signals are stored into the first, second, . . . , and n-thareas 119(1), 119(2), . . . , and 119(n) of the track buffer memory 119at the respective transfer rates R1, R2, . . . , and Rn lower than thepredetermined constant transfer rate Rp. The first, second, . . . , andn-th information signals are transmitted from the first, second, . . . ,and n-th areas 119(1), 119(2), . . . , and 119(n) of the track buffermemory 119 to the optical head 114 at the predetermined constanttransfer rate Rp. The optical head 114 records the first, second, . . ., and n-th information signals on the first, second, . . . , and n-thareas 113(1), 113(2), . . . , and 113(n) of the optical disc 113 on atime sharing basis.

[0317] A third mode of operation of the apparatus 110 is executed in thecase where the optical disc 113 is of the rewritable type. During thethird mode of operation, the optical head 114 reproduces at least oneinformation signal from first one of the first, second, . . . , and n-thareas 113(1), 113(2), . . . , and 113(n) of the optical disc 113. Thereproduced information signal is transmitted from the optical head 114to the track buffer memory 119. The reproduced information signal isstored into the track buffer memory 119 at the predetermined constanttransfer rate Rp. The reproduced information is transmitted from thetrack buffer memory 119 at the related transfer rate lower than thepredetermined constant transfer rate Rp. During the third mode ofoperation, another information signal (an information signal to berecorded) is stored into the track buffer memory 119 at the relatedtransfer rate lower than the predetermined constant transfer rate Rp.The recorded information signal is transmitted from the track buffermemory 119 to the optical head 114 at the predetermined constanttransfer rate Rp. The optical head 114 records the transmittedinformation signal on second one of the first, second, . . . , and n-thareas 113(1), 113(2), . . . , and 113(n) of the optical disc 113. Thesignal reproduction by the optical head 114 and the signal recording bythe optical head 114 alternate with each other on a time sharing basis.

[0318] As previously indicated, the rate of the transfer of the first,second, . . . , and n-th information signals by the optical head 114 isdenoted by “Rp” (Mbps). Regarding the track buffer memory 119, the rateof the transfer of the first information signal is denoted by “R1”(Mbps). The rate of the transfer of the second information signal isdenoted by “R2” (Mbps). Similarly, the rates of the transfer of thethird and later information signals are denoted by “R3”, . . . (Mbps).The rate of the transfer of the n-th information signal is denoted by“Rn” (Mbps). The minimum capacity of the track buffer memory 119 isdenoted by “Ym” (Mbits). The size (the total number of bits) of thefirst information signal recorded on each of the sub-areas A1, A2, A3, .. . in the first area 113(1) of the optical disc 113 is denoted by “Y1”(Mbits). The size (the total number of bits) of the second informationsignal recorded on each of the sub-areas B1, B2, B3, . . . in the secondarea 113(2) of the optical disc 113 is denoted by “Y2” (Mbits).Similarly, the sizes of the third and later information signals aredenoted by “Y3”, . . . (Mbits). The size (the total number of bits) ofthe n-th information signal recorded on each of the sub-areas N1, N2,N3, . . . in the n-th area 113(n) of the optical disc 113 is denoted by“Yn” (Mbits). The seek time of movement of the optical head 114 from thefirst area 113(1) to the second area 113(2) in the optical disc 113 isdenoted by “S1” (s). The seek time of movement of the optical head 114from the second area 113(2) to the third area 113(3) in the optical disc113 is denoted by “S2” (s). Similarly, the seek time of movement of theoptical head 114 from present one to next one of the third and laterareas is denoted by “Sk” (s) where k=3, 4, 5, . . . . The seek time ofmovement of the optical head 114 from the n-th area 113(n) to the firstarea 113(1) in the optical disc 113 is denoted by “Sn” (s).

[0319] Each of the seek times S1, S2, . . . , and Sn is equal to a firsttime interval plus a second time interval. The first time intervalstarts from the moment at which the optical head 114 reaches areproduction end position and suspends the reproduction of aninformation signal from one area 113(1), 113(2), . . . , or 113(n) inthe optical disc 113. The first time interval ends and the second timeinterval starts when the optical head 114 moves to a next area in theoptical disc 113. The second time interval continues until the opticalhead 114 starts reproducing an information signal from the next area inthe optical disc 113. During the second time interval, a target addressof the next area in the optical disc 113 is found, and preparations forthe reproduction of the information signal therefrom have been made.

[0320] The sum ΣRn of the transfer rates R1, R2, . . . , and Rn for theinformation signals written into and read out from the track buffermemory 119 is smaller than the predetermined constant transfer rate Rprelated to the optical head 114. Thus, the transfer rates R1, R2, . . ., and Rn, and the predetermined constant transfer rate Rp are in thefollowing relation.

Rp>R 1+R 2+ . . . +Rn  (31)

[0321] The recording or playback time T1 (S) for which the optical head114 continuously records or reproduces the first information signal onor from the first area 113(1) of the optical disc 113 is given asfollows.

T 1=Y 1/Rp  (32)

[0322] The recording or playback time T2 (S) for which the optical head114 continuously records or reproduces the second information signal onor from the second area 113(2) of the optical disc 113 is given asfollows.

T 2=Y 2/Rp  (33)

[0323] Similarly, the recording or playback time Tk (S) for which theoptical head 114 continuously records or reproduces the k-th informationsignal on or from the k-th area 113(k) of the optical disc 113 is givenas follows.

Tk=Yk/Rp where k=3, 4, 5,

[0324] The recording or playback time Tn (S) for which the optical head114 continuously records or reproduces the n-th information signal on orfrom the n-th area 113(2) of the optical disc 113 is given as follows.

Tn=Yn/Rp  (34)

[0325] Regarding the transfer rates Rp, R1, R2, . . . , and Rn, thefollowing ratio is considered.

Rp/(Rp−R1−R2−Rn)  (35)

[0326] where “Rp” corresponds to a 1-cycle time during which the first,second, . . . , and n-th information signals are sequentially recordedor reproduced once, and “(Rp−R1−R2− . . . Rn)” corresponds to a seekperiod in the 1-cycle time.

[0327] Regarding the times Ti, T2, . . . , and Tn, S1, S2, . . . , andSn, the following ratio is considered.

(T1+S1+T2+S2 . . . +Tn+Sn)/(S1+S2 . . . +Sn)  (36)

[0328] where “(T1+S1+T2+S2 . . . +Tn+Sn)” corresponds to a 1-cycle timeduring which the first, second, . . . , and n-th information signals aresequentially recorded or reproduced once, and “(S1+S2 . . . +Sn)”corresponds to a total seek period in the 1-cycle time.

[0329] The ratio in the relation (35) and the ratio in the relation (36)are equal to each other, and the following relation is available.

Rp/(Rp−R 1−R 2 . . . Rn)=(T 1+S 1+T 2+S 2 . . . +Tn+Sn)/(S 1+S 2 . . .+Sn)  (37)

[0330] The equation (37) is changed into the following version.

(T 1+T 2 . . . +Tn)=(R 1+R 2 . . . +Rn)·(S 1+S 2 . . . +Sn)/(Rp−R 1−R 2. . . Rn)  (38)

[0331] Combining the equations (32) and (33) with the equation (38)results in the following equation.

(Y 1+Y 2 . . . +Yn)=Rp·(R 1+R 2 . . . +Rn)·(S 1+S 2 . . . +Sn)/(Rp−R 1−R2 . . . Rn)  (39)

[0332] The rate Rp of the transfer of the first, second, . . . , andn-th information signals between the optical disc 113 and the trackbuffer memory 119 is equal to the predetermined constant value. Thepredetermined constant transfer rate Rp is higher than the transferrates R1, R2, . . . , and Rn for the first, second, . . . , and nthinformation signals in connection with the track buffer memory 119.During the recording of the first, second, . . . , and n-th informationsignals, the transfer rates R1, R2, . . . , and Rn are decided on thebasis of the user's setting (the user's selection). During the playbackof the first, second, . . . , and n-th information signals, the transferrates R1, R2, . . . , and Rn are decided on the basis of the recordingconditions stored in the optical disc 113 as control data. For example,the control data are contained in management information stored in themanagement area 113 x of the optical disc 113. The seek times S1, S2, .. . , and Sn are determined according to the specifications of theapparatus 110 and the addresses on the optical disc 113. To implementcontinuous recording or continuous playback of the information-signalcontents, the sum ΣYn of the size (the total number of bits) Y1 of thefirst information signal on each of the sub-areas in the first area113(1) of the optical disc 113, the size (the total number of bits) Y2of the second information signal on each of the sub-areas in the secondarea 113(2) of the optical disc 113, . . . , and the size (the totalnumber of bits) Yn of the n-th information signal on each of thesub-areas in the n-th area 113(n) of the optical disc 113 is chosen tosatisfy a relation (40) as follows. $\begin{matrix}{\left( {{Y1} + {{Y2}\quad \cdots} + {Yn}} \right) \geqq {{Rp} \cdot \left( {{R1} + {R2\cdots} + {Rn}} \right) \cdot {\left( {{S1} + {{S2\cdots}\quad {Sn}}} \right)/\left( {{Rp} - {R1} - {{R2\cdots}\quad {Rn}}} \right)}}} & (40)\end{matrix}$

[0333] The relation (40) is rewritten as follows.

ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣPn)  (41)

[0334] where:

[0335] ΣYn=Y1+Y2 . . . +Yn

[0336] ΣRn=R1+R2 . . . +Rn

[0337] ΣSn=S1+S2 . . . +Sn

[0338] When each of the seek times S1, S2, . . . , and Sn is set to anallowable seek time S equal to a fixed time taken by the optical head114 to move between an innermost part and an outermost part of theoptical disc 113, the following equation is satisfied.

ΣSn=n·S  (42)

[0339] Combining the equation (42) with the relation (41) results in thefollowing equation.

ΣYn≧Rp·ΣRn·n·S/(Rp−ΣRn)  (43)

[0340] In the case where the optical disc 113 is of the rewritable DVDtype, the allowable seek time S is set to about 1.5 seconds.

[0341] The sizes Y1, Y2, . . . , and Yn, and the transfer rates R1, R2,. . . , and Rn are in the following relations.

Y 1≧Rp·R 1·(S 1+S 2 . . . +Sn)/(Rp−R 1−R 2 . . . Rn)  (44)

Y 2≧Rp·R 2·(S 1+S 2 . . . +Sn)/(Rp−R 1−R 2 . . . Rn)  (45)

[0342] ... ... ...

[0343] ... ... ...

Yn≧Rp·Rn·(S 1+S 2 . . . +Sn)/(Rp−R 1−R 2 . . . Rn)  (46)

[0344] Thus, in the case where the transfer rates Rp, R1, R2, . . . ,and Rn and the seek times S1, S2, . . . , and Sn are decided, continuousrecording or continuous playback of the contents of the “n” informationsignals can be implemented when the sizes Y1, Y2, . . . , and Yn arechosen to satisfy the above-indicated relations (40), (41), (43), (44),(45), and (46). The recording or playback times T1, T2, . . . , and Tnare determined as the sizes Y1, Y2, . . . , and Yn and the transferrates Rp, R1, R2, . . . , and Rn are decided.

[0345] In addition, the sum ΣYn of the sizes Y1, Y2, . . . , and Yn, themaximum size of the track buffer memory 119, and the empty value and thefull value related to each of the first, second, . . . , and n-th areas119(1), 119(2), . . . , and 119(n) are decided according to therelations (40), (41), (43), (44), (45), and (46).

[0346] The minimum capacity Ym of the track buffer memory 119 satisfiesthe following relation (47).

Ym>Rp·ΣRnΣSn/(Rp−ΣRn)  (47)

[0347] When each of the seek times S1, S2, . . . , and Sn is set to theallowable seek time S, the relation (47) is rewritten as follows.

Ym>Rp·ΣRn·n·S/(Rp−ΣRn)  (48)

[0348] It should be noted that a portion of the buffer memory 121connected to the audio-video encoding and decoding unit 120 may be usedas a track buffer memory substituting for the track buffer memory 119.

[0349] In the case where the optical head 114 is required to record the“n” information signals on the optical disc 113 on a time sharing basis,conditions of unoccupied portions of the areas 113(1)-113(n) in theoptical disc 113 are detected. Specifically, the management area 113 xin the optical disc 113 is accessed. Start addresses and end addressesof unoccupied regions are calculated on the basis of the start addressesand the end addresses of data-loaded regions which are stored in themanagement area 113 x. Then, the sizes and the positions of theunoccupied regions are calculated. For each of the 2-Mbps, 4-Mbps, and8-Mbps transfer rates concerning the “n” information signals, a decisionis made as to whether or not the size of each unoccupied region issufficient to implement continuous recording. In addition, the seek timeof the optical head 114 is calculated as follows. The difference betweenaddresses is calculated. The movement-corresponding track number iscomputed on the basis of the address difference by referring to a seektable provided in the program ROM within the system controller 122. Thecomputation of the movement-corresponding track number is also based onthe fact that the rotation of the optical disc 113 undergoes CLVcontrol. Given calculation using the movement-corresponding track numberand a given coefficient provides a calculated seek time of the opticalhead 114. It should be noted that the seek time of the optical head 114may be set to a given value depending on the type of the apparatus 110or a standards-based allowable seek time.

[0350] Multiple-Signal Playback Mode

[0351] A multiple-signal playback mode of operation of the apparatus 110is executed in the case where the optical disc 113 is designedexclusively for playback. During the multiple-signal playback mode ofoperation, the optical head 114 reproduces the “n” information signalsfrom the optical disc 113 on a time sharing basis while the contents ofthe “n” information signals are continuously played back.

[0352] The optical disc 113 has the first area 113(1) divided into thesub-areas on which the blocks of the first information signal arepreviously recorded respectively. In addition, the optical disc 113 hasthe second area 113(2) divided into the sub-areas on which the blocks ofthe second information signal are previously recorded respectively.Similarly, the optical disc 113 has the third and later areas 113(3) . .. on which the third and later information signals are previouslyrecorded. Furthermore, the optical disc 113 has the n-th area 113(n)divided into the sub-areas on which the blocks of the n-th informationsignal are previously recorded respectively. Each of the blocks of thefirst information signal has a predetermined size (a predetermined totalnumber of bits) Y1. Each of the blocks of the second information signalhas a predetermined size (a predetermined total number of bits) Y2.Similarly, the blocks of the third and later information signals havepredetermined sizes Y3 . . . . Each of the blocks of the n-thinformation signal has a predetermined size (a predetermined totalnumber of bits) Yn.

[0353] When the multiple-signal playback mode of operation is started,the optical head 114 reproduces management information from themanagement area 113 x in the optical disc 113. The reproduced managementinformation is transmitted from the optical head 114 to the systemcontroller 122. The system controller 122 detects the locations andconditions of the sub-areas in the areas 113(1)-113(n) from themanagement information. Generally, the system controller 122 alsoderives information of transfer rates R1, R2, . . . , and Rn from themanagement information. Then, the optical head 114 is moved to aposition corresponding to the sub-area A1 in the first area 113(1) ofthe optical disc 113. The optical head 114 reproduces the firstinformation signal from the sub-area Al in the optical disc 113. Thereproduced first information signal is transmitted from the optical head114 to the track buffer memory 119, being stored into the first area119(1) in the track buffer memory 119 at the predetermined constanttransfer rate Rp.

[0354] As shown in FIG. 23, after the degree of occupancy of the firstarea 119(1) in the track buffer memory 119 reaches the related emptyvalue, the first information signal is read out from the memory area119(1) toward the audio-video encoding and decoding unit 120 at thetransfer rate R1 and the first information signal is transmitted fromthe sub-area A1 in the optical disc 113 to the memory area 119(1) at thepredetermined constant transfer rate Rp. Thus, during this stage, thedegree of occupancy of the memory area 119(1) increases at a ratecorresponding to “Rp−R1”.

[0355] When the degree of occupancy of the memory area 119(1) reachesthe related full value, the transmission of the first information signalfrom the sub-area Al in the optical disc 113 to the memory area 119(1)is suspended. Then, the optical head 114 is moved to a positioncorresponding to the sub-area B1 in the second area 113(2) of theoptical disc 113. The seek time S1 related to this movement of theoptical head 114 is equal to or shorter than 1.5 seconds. The opticalhead 114 transmits the second information signal from the sub-area B1 inthe optical disc 113 to the second area 119(2) of the track buffermemory 119 at the predetermined constant transfer rate Rp. Even afterthe degree of occupancy of the memory area 119(1) reaches the relatedfull value, the first information signal continues to be read out fromthe memory area 119(1) at the transfer rate R1. Thus, during this stage,the degree of occupancy of the memory area 119(1) decreases at a ratecorresponding to “R1”. The read-out of the first information signal fromthe memory area 119(1) is completed before the optical head 114 accessesthe sub-area A2 in the first area 113(1) of the optical disc 113.

[0356] After the degree of occupancy of the second area 119(2) in thetrack buffer memory 119 reaches the related empty value, the secondinformation signal is read out from the memory area 119(2) toward theaudio-video encoding and decoding unit 120 at the transfer rate R2 andthe second information signal continues to be transmitted from thesub-area B1 in the optical disc 113 to the memory area 119(2) at thepredetermined constant transfer rate Rp. Thus, during this stage, thedegree of occupancy of the memory area 119(2) increases at a ratecorresponding to “Rp−R2”.

[0357] When the degree of occupancy of the memory area 119(2) reachesthe related full value, the transmission of the second informationsignal from the sub-area B1 in the optical disc 113 to the memory area119(2) is suspended. Then, the optical head 114 is moved to a positioncorresponding to the first sub-area in the third area 113(3) of theoptical disc 113. The seek time S2 related to this movement of theoptical head 114 is equal to or shorter than 1.5 seconds. Even after thedegree of occupancy of the memory area 119(2) reaches the related fullvalue, the second information signal continues to be read out from thememory area 119(2) at the transfer rate R2. Thus, during this stage, thedegree of occupancy of the memory area 119(2) decreases at a ratecorresponding to “R2”. The read-out of the second information signalfrom the memory area 119(2) is completed before the optical head 114accesses the sub-area B2 in the second area 113(2) of the optical disc113.

[0358] The above-mentioned sequence of steps is iterated while theoptical head 114 sequentially reproduces the third and later informationsignals from the first sub-areas in the third and later areas113(3)-113(n) of the optical disc 113. After the reproduction of then-th information signal from the sub-area N1 in the n-th area 113(n) ofthe optical disc 113 is completed, the optical head 114 is moved to aposition corresponding to the sub-area A2 in the first area 113(1) ofthe optical disc 113. During a subsequent term, such processes areiterated. Thus, the contents of the “n” information signals arecontinuously played back while the optical head 114 sequentiallyaccesses the sub-areas in the areas 113(1)-113(n) of the optical disc113 in the order as “A1, B1, . . . , N1, A2, B2, . . . , N2 . . .”.During the multiple-signal playback mode of operation of the apparatus110, the previously-indicated parameters satisfy the relations(31)-(48).

[0359] Multiple-Signal Recording Mode

[0360] A multiple-signal recording mode of operation of the apparatus110 is executed in the case where the optical disc 113 is of therewritable type. During the multiple-signal recording mode of operation,the “n” information signals are written into the areas 119(1)-119(n) inthe track buffer memory 119 at the transfer rates R1−Rn, respectively.The “n” information signals are transmitted from the areas 119(1)-119(n)in the track buffer memory 119 to the optical head 114 on a time sharingbasis at the predetermined constant transfer rate Rp higher than thetransfer rates R1−Rn. The optical head 114 records the “n” informationsignals on the areas 113(1)-113(n) in the optical disc 113 on a timesharing basis, respectively.

[0361] The optical disc 113 is previously provided with the first area113(1) divided into the sub-areas for storing the respective blocks ofthe first information signal. The sub-areas in the first area 113(1)have the predetermined size Y1. In addition, the optical disc 113 ispreviously provided with the second area 113(2) divided into thesub-areas for storing the respective blocks of the second informationsignal. The sub-areas in the second area 113(2) have the predeterminedsize Y2. Similarly, the optical disc 113 is previously provided with thethird and later areas 113(3) . . . for storing the third and laterinformation signals. Furthermore, the optical disc 113 is previouslyprovided with the n-th area 113(n) divided into the sub-areas forstoring the respective blocks of the nth information signal. Thesub-areas in the n-th area 113(n) have the predetermined size Yn. Inaddition, the optical disc 113 has the management area 113 x loaded withthe management information representing the locations and conditions ofthe sub-areas in the areas 113(1)-113(n). Unoccupied regions in theoptical disc 113 can be detected from the management information.

[0362] During the multiple-signal recording mode of operation of theapparatus 110, the audio-video encoding and decoding unit 120 encodes“n” original signals into the “n” information signals respectively. The“n” information signals are transferred from the audio-video encodingand decoding unit 120 to the track buffer memory 119 at the rates R1−Rn,respectively. The rates R1−Rn of the transfer of the “n” informationsignals from the audio-video encoding and decoding unit 120 to the trackbuffer memory 119 can be selected from among different values accordingto user's operation of the key input unit 123. The different valuesinclude a transfer rate of 8 Mbps which corresponds to a recording timeof 2 hours and a high picture quality, a transfer rate of 4 Mbps whichcorresponds to a recording time of 4 hours and a slightly high picturequality, and a transfer rate of 2 Mbps which corresponds to a recordingtime of 8 hours and a normal picture quality. A transfer rate of 17 Mbpsmay be added to the candidate values. The “n” information signals aretemporarily stored in the areas 119(1)-119(n) in the track buffer memory119, respectively. At an initial stage, the optical head 114 is in astand-by state or a kick wait state while being located at a positioncorresponding to a target track on the optical disc 113. The systemcontroller 122 always monitors the degree of occupancy of each of thememory areas 119(1)-119(n) which varies between the related empty valueand the related full value under normal conditions. When the degrees ofoccupancy of the memory areas 119(1)-119(n) reach the related fullvalues, the “n” information signals start to be read out from the memoryareas 119(1)-119(n) on a time sharing basis and at the predeterminedconstant transfer rate Rp higher than the transfer rates R1−Rn. Theoptical head 114 records the “n” read-out information signals on theareas 113(1)-113(n) of the optical disc 113 respectively on a timesharing basis and at the predetermined constant transfer rate Rp. Inthis way, the continuously recording of the original signals isimplemented.

[0363] When the multiple-signal recording mode of operation is started,the optical head 114 reproduces management information from themanagement area 113 x in the optical disc 113. The reproduced managementinformation is transmitted from the optical head 114 to the systemcontroller 122. The system controller 122 detects unoccupied regions inthe areas 113(1)-113(n) of the optical disc 113 from the managementinformation. Then, the optical head 114 is moved to a positioncorresponding to the sub-area A1 in the first area 113(1) of the opticaldisc 113 provided that the sub-area A1 is found to be unoccupied. On theother hand, the first information signal is transmitted from theaudio-video encoding and decoding unit 120 to the track buffer memory119, and is stored into the first area 119(1) of the track buffer memoryat the transfer rate R1.

[0364] As shown in FIG. 24, after the degree of occupancy of the firstarea 119(1) in the track buffer memory 119 reaches the related fullvalue, the first information signal is transmitted from the memory area119(1) to the sub-area A1 in the optical disc 113 via the optical head114 at the predetermined constant transfer rate Rp and the firstinformation signal is stored into the memory area 119(1) from theaudio-video encoding and decoding unit 120 at the transfer rate RI.Thus, during this stage, the degree of occupancy of the memory area119(1) decreases at a rate corresponding to “Rp−R1”.

[0365] When the degree of occupancy of the memory area 119(1) reachesthe related empty value, the transmission of the first informationsignal from the memory area 119(1) to the sub-area Al in the opticaldisc 113 is suspended. Then, the optical head 114 is moved to a positioncorresponding to the sub-area B1 in the second area 113(2) of theoptical disc 113 provided that the sub-area B1 is found to beunoccupied. The seek time S1 related to this movement of the opticalhead 114 is equal to or shorter than 1.5 seconds. The second informationsignal is stored into the second area 119(2) of the track buffer memory119 from the audio-video encoding and decoding unit 120 at the transferrate R2. Even after the degree of occupancy of the memory area 119(1)reaches the related empty value, the first information signal continuesto be stored into the memory area 119(1) from the audio-video encodingand decoding unit 120 at the transfer rate R1. Thus, during this stage,the degree of occupancy of the memory area 119(1) increases at a ratecorresponding to “R1”. The degree of occupancy of the memory area 119(1)reaches the related full value before the optical head 114 accesses thesub-area A2 in the first area 113(1) of the optical disc 113.

[0366] After the degree of occupancy of the second area 119(2) in thetrack buffer memory 119 reaches the related full value, the secondinformation signal is transmitted from the memory area 119(2) to thesub-area B1 in the optical disc 113 via the optical head 114 at thepredetermined constant transfer rate Rp and the second informationsignal continues to be stored into the memory area 119(2) from theaudio-video encoding and decoding unit 120 at the transfer rate R2.Thus, during this stage, the degree of occupancy of the memory area119(2) decreases at a rate corresponding to “Rp−R2”.

[0367] When the degree of occupancy of the memory area 119(2) reachesthe related empty value, the transmission of the second informationsignal from the memory area 119(2) to the sub-area B1 in the opticaldisc 113 is suspended. Then, the optical head 114 is moved to a positioncorresponding to the first sub-area in the third area 113(3) of theoptical disc 113 provided that the first sub-area is found to beunoccupied. The seek time S2 related to this movement of the opticalhead 114 is equal to or shorter than 1.5 seconds. Even after the degreeof occupancy of the memory area 119(2) reaches the related empty value,the second information signal continues to be stored into the memoryarea 119(2) from the audio-video encoding and decoding unit 120 at thetransfer rate R2. Thus, during this stage, the degree of occupancy ofthe memory area 119(2) increases at a rate corresponding to “R2”. Thedegree of occupancy of the memory area 119(2) reaches the related fullvalue before the optical head 114 accesses the sub-area B2 in the secondarea 113(2) of the optical disc 113.

[0368] The above-mentioned sequence of steps is iterated while the thirdand later information signals are stored into the third and later areas119(3)-119(n) of the track buffer memory 119 from the audio-videoencoding and decoding unit 120 at the transfer rates R3−Rn. In addition,the third and later information signals are transmitted from the thirdand later areas 119(3)-119(n) of the track buffer memory 119 to theoptical head 114 at the predetermined constant transfer rate Rp on atime sharing basis. The optical head 114 sequentially records the thirdand later information signals on the first sub-areas in the third andlater areas 113(3)-113(n) of the optical disc 113. After the recordingof the n−1 th information signal on the sub-area N1 in the n-th area113(n) of the optical disc 113 is completed, the optical head 114 ismoved to a position corresponding to the sub-area A2 in the first area113(1) of the optical disc 113 provided that the sub-area A2 is found tobe unoccupied. During a subsequent term, such processes are iterated.Thus, the “n” original signals inputted into the audio-video encodingand decoding unit 120 are continuously recorded while the optical head114 sequentially accesses the sub-areas in the areas 113(1)-113(n) ofthe optical disc 113 in the order as “A1, B1, . . . , N1, A2, B2, . . ., N2, . . . ”. During the multiple-signal recording mode of operation ofthe apparatus 110, the previously-indicated parameters satisfy therelations (31)-(48).

[0369] In general, after the recording of the “n” information signals onthe optical disc 113 has been completed, information of the transferrates R1−Rn is recorded on the management area 113 x of the optical disc113 via the optical head 114.

[0370] Signal Recording/Playback Mode

[0371] A signal recording/playback mode of operation of the apparatus110 is executed in the case where the optical disc 113 is of therewritable type. During the signal recording/playback mode of operation,the optical head 114 reproduces at least one information signal fromfirst one of the areas 113(i)-113(n) in the optical disc 113 and recordsat least one information signal on second one of the areas 113(1)-113(n)in the optical disc 113 on a time sharing basis. The reproducedinformation signal is transmitted from the optical disc 114 to the trackbuffer memory 119. The reproduced information signal is written intocorresponding one of the areas 119(1)-i19(n) in the track buffer memory119 at the predetermined constant transfer rate Rp. The reproducedinformation signal is transmitted from the track buffer memory 119 tothe audio-video encoding and decoding unit 120 at corresponding one ofthe transfer rates R1−Rn. On the other hand, at least one informationsignal to be recorded is transmitted to the track buffer memory 119 fromthe audio-video encoding and decoding unit 120. The recorded informationsignal is written into corresponding one of the areas 119(1)-119(n) inthe track buffer memory 119 at corresponding one of the transfer ratesR1−Rn. The recorded information signal is transmitted from the trackbuffer memory 119 to the optical head 114 at the predetermined constanttransfer rate Rp. The optical head 114 records the transmittedinformation signal on corresponding one of the areas 113(1)-113(n) inthe optical disc 113.

[0372] During the signal recording/playback mode of operation, each ofthe seek times S1−Sn related to the optical head 114 is equal to orshorter than 1.5 seconds. In addition, the previously-indicatedparameters satisfy the relations (31)-(48).

[0373] It should be noted that the “n” information signals to berecorded or reproduced may be ranked according to priority. In the casewhere a seek error occurs or the transfer rates R1−Rn are changed sothat the relations (31)-(48) become unsatisfied, low-priorityinformation signals may be discarded or disregarded to maintaincontinuous recording or continuous playback of the contents ofhigh-priority information signals.

[0374] It should be noted that the apparatus 110 in FIG. 17 may bedivided into an optical disc drive, a solid-state memory unit, andanother unit. The solid-state memory unit is detachably connected withthe optical disc drive. Specifically, the solid-state memory unit isconnected with the optical disc drive via a disconnectable connector.The optical disc drive includes the spindle motor 111, the turntable112, the optical head 114, the driver 115, the amplifier unit 116, andthe servo unit 117. The solid-state memory unit includes the signalprocessor 118, the track buffer memory 119, and the system controller122. When the solid-state memory unit is disconnected from the opticaldisc drive, at least one of “n” information signals in the track buffermemory 119 can be played back via the signal processor 118 and theaudio-video encoding and decoding unit 120.

Sixth Embodiment

[0375]FIG. 25 shows an information-signal communication apparatus 130according to a sixth embodiment of this invention. The apparatus 130 inFIG. 25 is similar to the apparatus 110 in FIG. 17 except for designchanges indicated hereinafter.

[0376] The apparatus 130 in FIG. 25 includes a spindle motor 111, aturntable 112, an optical head (an optical pickup) 114, a driver 115, anamplifier unit 116, a servo unit 117, a signal processor 118, a trackbuffer memory 119, and a system controller 122. The devices 111, 112,114, 115, 116, 117, 118, 119, and 122 are connected in a manner similarto that in the apparatus 110 in FIG. 17. The apparatus 130 in FIG. 25further includes an ATAPI (AT attachment packet interface) unit 131,that is, an interface 131 of an ATAPI type. The interface 131 isconnected to the signal processor 118.

[0377] A host computer or an external apparatus 132 can be connectedwith the apparatus 130 in FIG. 25 via the interface 131. The externalapparatus 132 includes an audio-video encoding and decoding unit 120, amemory 121, and a host computer unit 132A. The memory 121 and the hostcomputer unit 132A are connected to the audio-video encoding anddecoding unit 120. The audio-video encoding and decoding unit 120 can beconnected with the signal processor 118 in the apparatus 130 via theinterface 131.

[0378] A satellite digital broadcasting reception antenna 141 isconnected to a satellite digital broadcasting decoder 142. The satellitedigital broadcasting decoder 142 is connected to a switch 143. A switch143 is connected to a stream converter 144. The switch 143 is connectedto the Internet via a terminal 145. The stream converter 144 can beconnected with the signal processor 118 in the apparatus 130 via theinterface 131. The satellite digital broadcasting decoder 142, theswitch 143, the stream converter 144, and the host computer unit 132Aare connected to each other.

[0379] In more detail, the ATAPI unit 131 includes an interface block.The audio-video encoding and decoding unit 120 includes an interfaceblock which can be connected with the interface block in the ATAPI unit131. The stream converter 144 includes an interface block which can beconnected with the interface block in the ATAPI unit 131. The apparatus132 can control the apparatus 130 while using control signals in the Mt.Fuji command system. The host computer unit 132A can control the switch143.

[0380] In the case where “n” information signals are required to berecorded, the host computer unit 132A in the apparatus 132 transmitsinformation of transfer rates R1−Rn for the “n” information signals(transfer-rate representing flags) to the apparatus 130 via theaudio-video encoding and decoding unit 120 and the interface 131. Theaudio-video encoding and decoding unit 120 in the apparatus 132transmits the “n” information signals to the signal processor 118 in theapparatus 130 via the interface 131. In addition, the host computer unit132A in the apparatus 132 transmits a recording start command signal anda recording start address signal to the apparatus 130 via theaudio-video encoding and decoding unit 120 and the interface 131.

[0381] In the case where “n” information signals are required to bereproduced from an optical disc 113, the host computer unit 132A in theapparatus 132 transmits a playback start command signal and a discaddress signal to the apparatus 130 via the audio-video encoding anddecoding unit 120 and the interface 131. The apparatus 130 reproduces asignal (for example, control data or management information) from aportion of the optical disc 113 whose position is designated by the discaddress signal. The host computer unit 132A in the apparatus 132receives the reproduced signal from the apparatus 130 via the interface131 and the audio-video encoding and decoding unit 120, and calculatestransfer rates R1−Rn on the basis of the reproduced signal. The hostcomputer unit 132A in the apparatus 132 transmits information of thecalculated transfer rates R1−Rn (transfer-rate representing flags) tothe apparatus 130 via the audio-video encoding and decoding unit 120 andthe interface 131. Then, the apparatus 130 reproduces the “n”information signals while using the transfer rates R1−Rn.

[0382] The interface 131 may be of an IEEE1394 type rather than theATAPI type. The interface 131 may be of a wireless type using a radiosignal or a light signal.

[0383] It should be noted that the apparatus 130 in FIG. 25 may bedivided into an optical disc drive, a solid-state memory unit, and asecond unit. The solid-state memory unit is detachably connected withthe optical disc drive and the interface 131 in the second unit.Specifically, the solid-state memory unit is connected with the opticaldisc drive and the interface 131 via disconnectable connectors. Theoptical disc drive includes the spindle motor 111, the turntable 112,the optical head 114, the driver 115, the amplifier unit 116, and theservo unit 117. The solid-state memory unit includes the signalprocessor 118, the track buffer memory 119, and the system controller122. When the solid-state memory unit is disconnected from the opticaldisc drive, at least one of “n” information signals in the track buffermemory 119 can be played back via the signal processor 118 and theaudio-video encoding and decoding unit 120.

Seventh Embodiment

[0384] A seventh embodiment of this invention is similar to the fifthembodiment or the sixth embodiment thereof except for design changesmentioned later.

[0385] During a recording mode of operation, the system controller 122periodically checks whether or not the relation (41) is satisfied. Whenthe system controller 122 finds that the relation (41) is not satisfied,the system controller 122 selects one of first, second, third, andfourth recording procedures and implements the selected recordingprocedure.

[0386] According to the first recording procedure, when the relation(41) is not satisfied, two or more information signals are selected fromamong “n” information signals. Non-selected information signals arediscarded or disregarded. With respect to the selected informationsignals, a decision is made as to whether or not the relation (41) issatisfied. In the case where the relation (41) is satisfied, theselected information signals are stored into corresponding ones of theareas 119(1)-119(n) in the track buffer memory 119 respectively. Theselected information signals are transferred from the track buffermemory 119 to the optical head 114 on a time sharing basis. The opticalhead 114 records the selected information signals on corresponding onesof the areas 113(1)-113(n) in the optical disc 113 respectively. Whenbeing recorded, the selected information signals may be weighted inresponse to the differences among the transfer rates for the selectedinformation signals, the channel position, or the genres of the contentsof the selected information signals on an automatic basis or a user'ssetting basis. The non-selected information signals are inhibited frombeing stored into the track buffer memory 119.

[0387] With reference to FIG. 26, four information signals “A”, “B”,“C”, and “D” compose input data. The information signal “A” is dividedinto blocks A1, A2, . . . . The information signal “B” is divided intoblocks B1, B2, . . . . The information signal “C” is divided into blocksC1, C2, . . . . The information signal “D” is divided into blocks D1, D2. . . . The blocks of the four information signals are multiplexed intothe input data in the order as “A1, B1, C1, D1, A2, B2, . . . ”.

[0388] According to the first recording procedure, when the relation(41) is not satisfied, two information signals “A” and “B” are selectedfrom among the four information signals. Regarding the selectedinformation signals “A” and “B”, a decision is made as to whether or notthe relation (41) is satisfied. In the case where the relation (41) issatisfied, the selected information signals are stored intocorresponding ones of the areas 119(1)-119(n) in the track buffer memory119 respectively. The non-selected information signals “C” and “D” areinhibited from being stored into the track buffer memory 119. Theselected information signals “A” and “B” are alternately transferredfrom the track buffer memory 119 to the optical head 114 on a timesharing basis. The optical head 114 records the selected informationsignals “A” and “B” on corresponding ones of the areas 113(1)-113(n) inthe optical disc 113 respectively. Specifically, the optical head 114records the block A1 of the information signal “A” on first one of thedisc areas 113(1)-113(n). Then, the optical head 114 executes seek andmoves from first one to second one of the disc areas 113(1)-113(n). Theoptical head 114 records the block B1 of the information signal “B” onsecond one of the disc areas 113(1)-113(n). Then, the optical head 114executes seek and moves from second one to first one of the disc areas113(1)-113(n). The optical head 114 records the block A2 of theinformation signal “A” on first one of the disc areas 113(1)-113(n).Such steps are reiterated. Accordingly, the blocks A1, A2, . . . of theinformation signal “A” are sequentially stored into first one of thedisc areas 113(1)-113(n). The blocks B1, B2, . . . of the informationsignal “B” are sequentially stored into second one of the disc areas113(1)-113(n).

[0389] According to the second recording procedure, when the relation(41) is not satisfied, two or more information signals are selected fromamong “n” information signals. The selected information signals arereferred to as the first selected information signals. Non-selectedinformation signals are discarded or disregarded. Two of the firstselected information signals are combined into one selected informationsignal. This selected information signal and the remaining firstselected information signal or signals are referred to as the secondselected information signals. With respect to the second selectedinformation signals, a decision is made as to whether or not therelation (41) is satisfied. In the case where the relation (41) issatisfied, the first selected information signals are stored intocorresponding ones of the areas 119(1)-l19(n) in the track buffer memory119 respectively. The first selected information signals are transferredfrom the track buffer memory 119 to the optical head 114 on a timesharing basis while two of the first selected information signals arecombined into one selected information signal. Thus, the optical head114 receives the second selected information signals from the trackbuffer memory 119. The optical head 114 records the second selectedinformation signals on ones of the areas 113(1)-113(n) in the opticaldisc 113 respectively.

[0390] With reference to FIG. 27, four information signals “A”, “B”,“C”, and “D” compose input data. The information signal “A” is dividedinto blocks A1, A2, . . . . The information signal “B” is divided intoblocks B1, B2, . . . . The information signal “C” is divided into blocksC1, C2, . . . . The information signal “D” is divided into blocks D1,D2, . . . . The blocks of the four information signals are multiplexedinto the input data in the order as “A1, B1, C1, D1, A2, B2, . . . ”.

[0391] According to the second recording procedure, when the relation(41) is not satisfied, three information signals “A”, “B”, and “C” areselected from among the four information signals. The selectedinformation signals “B” and “C” are combined into and handled as oneselected information signal “B+C”. Regarding the selected informationsignals “A” and “B+C”, a decision is made as to whether or not therelation (41) is satisfied. In the case where the relation (41) issatisfied, the selected information signals “A”, “B”, and “C” (theselected information signals “A”, and “B+C”) are stored intocorresponding ones of the areas 119(1)-119(n) in the track buffer memory119 respectively. The non-selected information signal “D” is inhibitedfrom being stored into the track buffer memory 119. The selectedinformation signals “A” and “B+C” are alternately transferred from thetrack buffer memory 119 to the optical head 114 on a time sharing basis.The optical head 114 records the selected information signals “A” and“B+C” on ones of the areas 113(1)-113(n) in the optical disc 113.Specifically, the optical head 114 records the block A1 of theinformation signal “A” on first one of the disc areas 113(1)-113(n).Then, the optical head 114 executes seek and moves from first one tosecond one of the disc areas 113(1)-113(n). The optical head 114 recordsthe blocks B1 and C1 of the information signals “B” and “C” on secondone of the disc areas 113(1)-113(n). Then, the optical head 114 executesseek and moves from second one to first one of the disc areas113(1)-113(n). The optical head 114 records the block A2 of theinformation signal “A” on first one of the disc areas 113(1)-113(n).Such steps are reiterated. Accordingly, the blocks A1, A2, . . . of theinformation signal “A” are sequentially stored into first one of thedisc areas 113(1)-113(n). The blocks B1, C1, B2, C2, . . . of theinformation signals “B” and “C” are sequentially stored into second oneof the disc areas 113(1)-113(n). This design results in a reduction ofthe total seek time related to the optical head 114.

[0392] According to the third recording procedure, when the relation(41) is not satisfied, “n” information signals are stored intocorresponding ones of the areas 119(1)-119(n) in the track buffer memory119 respectively. The “n” information signals are transferred from thetrack buffer memory 119 to the optical head 114 on a time sharing basis.The optical head 114 records the “n” information signals on one commonarea (for example, one of the areas 113(1)-113(n)) in the optical disc113. Since the optical head 114 does not move among the areas113(1)-113(n) in the optical disc 113, the total seek time related tothe optical head 114 can be reduced.

[0393] With reference to FIG. 28, four information signals “A”, “B”,“C”, and “D” compose input data. The information signal “A” is dividedinto blocks A1, A2, . . . . The information signal “B” is divided intoblocks B1, B2, . . . . The information signal “C” is divided into blocksC1, C2, . . . . The information signal “D” is divided into blocks D1,D2, . . . . The blocks of the four information signals are multiplexedinto the input data in the order as “A1, B1, C1, D1, A2, B2, . . . ”.

[0394] According to the third recording procedure, when the relation(41) is not satisfied, the four information signals “A”, “B”, “C”, and“D” are stored into corresponding ones of the areas 119(1)-119(n) in thetrack buffer memory 119 respectively. The four information signals “A”,“B”, “C”, and “D” are transferred from the track buffer memory 119 tothe optical head 114 on a time sharing basis, The optical head 114records the four information signals “A”, “B”, “C”, and “D” on onecommon area (for example, one of the areas 113(1)-113(n)) in the opticaldisc 113. Specifically, the optical head 114 sequentially records theblocks of the information signals “A”, “B”, “C”, and “D” on the commondisc area in the order as “A1, B1, C1, D1, A2, B2, . . . ”.

[0395] According to the fourth recording procedure, when the relation(41) is not satisfied, “n” information signals are stored intocorresponding ones of the areas 119(1)-119(n) in the track buffer memory119 respectively. Each of the memory areas 119(1)-119(n) can store twoor more blocks of the related information signal. Plural block cycles ofthe “n” information signals are held in the track buffer memory 119. The“n” information signals are transferred from the track buffer memory 119to the optical head 114 on a time sharing basis. The order in which theblocks of the “n” information signals are read out from the track buffermemory 119 differs from that occurring in the writing into the trackbuffer memory 119. In other words, the blocks of the “n” informationsignals are rearranged by the track buffer memory 119. The optical head114 records the “n” information signals on one common area (for example,one of the areas 113(1)-113(n)) in the optical disc 113. Since theoptical head 114 does not move among the areas 113(1)-113(n) in theoptical disc 113, the total seek time related to the optical head 114can be reduced.

[0396] With reference to FIG. 29, four information signals “A”, “B”,“C”, and “D” compose input data. The information signal “A” is dividedinto blocks A1, A2, . . . . The information signal “B” is divided intoblocks B1, B2, . . . . The information signal “C” is divided into blocksC1, C2, . . . . The information signal “D” is divided into blocks D1,D2, . . . . The blocks of the four information signals are multiplexedinto the input data in the order as “A1, B1, C1, D1, A2, B2, . . . ”.

[0397] According to the fourth recording procedure, when the relation(41) is not satisfied, the four information signals “A”, “B”, “C”, and“D” are stored into corresponding ones of the areas 119(1)-119(n) in thetrack buffer memory 119 respectively. The blocks of the four informationsignals “A”, “B”, “C”, and “D” are sequentially written into the trackbuffer memory 119 in the order as “A1, B1, C1, D1, A2, B2, . . . ”.Plural block cycles of the “n” information signals are held in the trackbuffer memory 119. The four information signals “A”, “B”, “C”, and “D”are transferred from the track buffer memory 119 to the optical head 114on a time sharing basis. The track buffer memory 119 rearranges theblocks of the four information signals “A”, “B”, “C”, and “D”.Specifically, the blocks of the four information signals “A”, “B”, “C”,and “D” are sequentially read out from the track buffer memory 119 inthe order as “A1, A2, B1, B2, C1, C2, D1, D2, A3, A4, . . . ”. Theoptical head 114 records the four information signals “A”, “B”, “C”, and“D” on one common area (for example, one of the areas 113(1)-113(n)) inthe optical disc 113. Specifically, the optical head 114 sequentiallyrecords the blocks of the information signals “A”, “B”, “C”, and “D” onthe common disc area in the order as “A1, A2, B1, B2, C1, C2, D1, D2,A3, A4, . . . ”.

[0398] One recording procedure is selected from among the first, second,third, and fourth recording procedures in response to the result ofcalculation concerning the relation (41) or in response to user'srequirement. Conditions of the selection include the followingconditions {circle over (1)}, {circle over (2)}, {circle over (3)},{circle over (4)}, {circle over (2)}, and {circle over (6)}.

[0399] {circle over (1)} Regarding the “n” information signals, adecision is made as to whether or not the relation (41) is satisfied.When it is decided that the relation (41) is not satisfied, at least twoof the “n” information signals are selected. Regarding the selectedinformation signals, a decision is made as to whether or not therelation (41) is satisfied. When it is decided that the relation (41) issatisfied, the first or second recording procedure is selected. On theother hand, when it is decided that the relation (41) is not satisfied,the third or fourth recording procedure is selected.

[0400] {circle over (2)} At an initial stage, the user selects one fromamong the first, second, third, and fourth recording procedures byoperating the key input unit 123. For example, in the case where thefirst recording procedure is initially selected, a decision is made asto whether or not the relation (41) is satisfied. When it is decidedthat the relation (41) is satisfied, the system controller 122 controlsthe display 125 via the audio-video encoding and decoding unit 120 andthe NTSC encoder 124 to indicate that the first, second, third, andfourth recording procedures are selectable. Then, the user finallyselects one from among the first, second, third, and fourth recordingprocedures. On the other hand, when it is decided that the relation (41)is not satisfied, the system controller 122 controls the display 125 viathe audio-video encoding and decoding unit 120 and the NTSC encoder 124to indicate that the third and fourth recording procedures areselectable. Then, the user finally selects one from among the third andfourth recording procedures.

[0401] {circle over (3)} One recording procedure is automaticallyselected from among the first, second, third, and fourth recordingprocedures in response to the types of the “n” information signals orthe types of the signal sources. When the “n” information signals arefed from the audio-video encoding and decoding unit 120, the first orsecond recording procedure is selected. When the “n” information signalsare “n” compression-resultant information signals composing a transportstream signal and transmitted from the satellite or the Internet, thethird or fourth recording procedure is selected. The signal recordingmay be responsive to the differences among the transfer rates for theinformation signals, the channel position, or the genres of the contentsof the information signals on a user's setting basis.

[0402] {circle over (4)} When the apparatus is driven by an AC powersupply, the first or second recording procedure is selected. When theapparatus is driven by a battery, the third or fourth recordingprocedure is selected. The track buffer memory 119 may be replaceable.When the capacity of the track buffer memory 119 exceeds a referencevalue, the first or second recording procedure is selected. When thecapacity of the track buffer memory 119 does not exceed the referencevalue, the third or fourth recording procedure is selected.

[0403] {circle over (5)} The system controller 122 detects the type ofthe optical disc 113. When the optical disc 113 is a DVD-RAM, the firstor second recording procedure is selected. When the optical disc 113 isa DVD-RW, the third or fourth recording procedure is selected.

[0404] {circle over (6)} The management information is reproduced fromthe management area 113 x in the optical disc 113. The system controller122 decides the conditions of unoccupied regions in the optical disc 113on the basis of the reproduced management information. In the presenceof unoccupied regions greater in size than a reference value, the firstor second recording procedure is selected. In the absence of such greatunoccupied regions, the third or fourth recording procedure is selected.

Eighth Embodiment

[0405]FIG. 30 shows an information-signal recording and reproducingapparatus 10F according to an eighth embodiment of this invention. Theapparatus 10F in FIG. 30 is similar to the apparatus 10A in FIG. 1except for design changes indicated hereinafter.

[0406] The apparatus 10F in FIG. 30 includes an NTSC encoder 224 and adisplay 225. The NTSC encoder 224 is connected to an audio-videoencoding and decoding unit 20. The display 225 is connected to the NTSCencoder 224. The apparatus 10F in FIG. 30 includes a system controller22F which replaces the system controller 22 (see FIG. 1). Originalinformation signals for a first information signal “A” and a secondinformation signal “B” can be fed to the audio-video encoding anddecoding unit 20 via input terminals 226 and 227, respectively.

[0407] During a playback mode of operation of the apparatus 10F, theaudio-video encoding and decoding unit 20 outputs an analog audio signaland an analog video signal to the NTSC converter 224. The analog audiosignal passes through the NTSC converter 224 before being applied toloudspeakers provided in the body of the display 225. The NTSC converter224 changes the analog video signal into a corresponding NTSC videosignal. The NTSC converter 224 outputs the NTSC video signal to thedisplay 225.

[0408] The apparatus 10F operates on an optical disc 13F. As shown inFIG. 31, an innermost portion or an inner portion of the optical disc13F has a management area 13 c for storing management information. Asshown in FIG. 32, the management area 13 c is divided into separatesub-areas which are given addresses C1, C2, C3, . . . , respectively.Thus, the sub-areas in the management area 13 c are also referred to asthe sub-areas C1, C2, C3, . . . . In the case where first areas 13 a andsecond areas 13 b of the optical disc 13F store a first informationsignal “A” and a second information signal “B”, the management area 13 cis loaded with management information including copyright information,title information, signals representative of transfer rates Ra and Rb,and signals representative of start addresses and end addresses for thefirst and second information signals “A” and “B”. In the case where thefirst areas 13 a and the second areas 13 b are unoccupied and do notstore the first and second information signals “A” and “B”, themanagement area 13 c is loaded with management information includingsignals representative of the start addresses and the end addresses ofthe unoccupied regions (the unoccupied areas).

[0409] In the case where the apparatus 10F is required to record thefirst and second information signals “A” and “B” on the optical disc13F, the system controller 22F operates to read out managementinformation from the management area 13 c of the optical disc 13F. Thesystem controller 22F detects conditions of unoccupied regions in thefirst and second areas 13 a and 13 b of the optical disc 13F byreferring to the read-out management information.

[0410] Also, in the case where the apparatus 10F is required to recordone of the first and second information signals “A” and “B” on theoptical disc 13F and to reproduce the other information signal from theoptical disc 13F, the system controller 22F operates to read outmanagement information from the management area 13 c of the optical disc13F. The system controller 22F detects conditions of unoccupied regionsin ones of the first and second areas 13 a and 13 b of the optical disc13F by referring to the read-out management information.

[0411] Specifically, the system controller 22F detects the startaddresses and the end addresses of unoccupied regions from the startaddresses and the end addresses of data-loaded regions which are storedin the management area 13 c. The system controller 22F calculates thesizes of the unoccupied regions from the intervals between the startaddresses and the end addresses of the data-loaded regions. The systemcontroller 22F stores data representative of the detected positions (thedetected start addresses and the detected end addresses) and thecalculated sizes of the unoccupied regions into an internal memory. Foreach of the 2-Mbps, 4-Mbps, and 8-Mbps transfer rates concerning thefirst and second information signals “A” and “B”, the system controller22F decides whether or not the size of each unoccupied region issufficient to implement continuous recording or continuousrecording/playback. In addition, the system controller 22F calculatesthe seek time of an optical head 14 as follows. The difference betweenaddresses is calculated. The movement-corresponding track number iscomputed on the basis of the address difference by referring to a seektable provided in the program ROM within the system controller 22F. Thecomputation of the movement-corresponding track number is also based onthe fact that the rotation of the optical disc 13F undergoes CLVcontrol. Given calculation using the movement-corresponding track numberand a given coefficient provides a calculated seek time of the opticalhead 14. It should be noted that the seek time of the optical head 14may be set to a given value depending on the type of the apparatus 10For a standards-based allowable seek time. When the recording of only theinformation signal “A” is considered and hence the terms related to theinformation signal “B” are nullified, the previously-indicated relations(9) and (19) are changed into the following relations.

Ya≧Rp·Ra·(Tab+Tba)/(Rp−Ra)  (51)

Ya≧2·Rp·Ra·Tmax/(Rp−Ra)  (52)

[0412] Preferably, the relations (51) and (52) are satisfied to providethe continuity of the contents of the information signal “A” recorded onthe unoccupied regions in the optical disc 13F. The program ROM in thesystem controller 22F may store a table of the results ofpreviously-executed calculations of the relations (51) and (52). In thiscase, the table is accessed when the conditions determined by therelations (51) and (52) are required to be detected.

[0413] Regarding the recording of only the information signal “A” (onlyone of the information signals “A” and “B”), the system controller 22Fcalculates the total size of the unoccupied regions in the optical disc13F. For each of the 2-Mbps, 4-Mbps, and 8-Mbps transfer rates, thesystem controller 22F calculates the recording time (or the recordingcapacity). For each of the 2-Mbps, 4-Mbps, and 8-Mbps transfer rates,the system controller 22F calculates the total size of usable portionsof the unoccupied regions in the optical disc 13F. For each of the2-Mbps, 4-Mbps, and 8-Mbps transfer rates, the system controller 22Fcalculates the region use efficiency (%) which is equal to the ratiobetween the total size of the unoccupied regions and the total size ofusable portions of the unoccupied regions in the optical disc 13F. Thesystem controller 22F controls the display 225 via the audio-videoencoding and decoding unit 20 and the NTSC encoder 224 to indicate thecalculated total size of the unoccupied regions in the optical disc 13F,the calculated recording times, the total sizes of usable portions ofthe unoccupied regions in the optical disc 13F, and the calculatedregion use efficiencies as shown in FIG. 33.

[0414] During a recording mode of operation of the apparatus 10F, afirst information signal “A” is inputted into a first area 19 a in atrack buffer memory 19 at a transfer rate Ra while a second informationsignal “B” is inputted into a second area 19 b in the track buffermemory 19 at a transfer rate Rb. The first and second informationsignals “A” and “B” are transmitted from the track buffer memory 19 tothe optical head 14 on a time sharing basis and at a predeterminedconstant transfer rate Rp higher than the transfer rates Ra and Rb. Theoptical head 14 records the first and second information signals “A” and“B” on unoccupied regions in the first and second areas 13 a and 13 b ofthe optical disc 13F. At an initial stage of the recording mode ofoperation, the system controller 22F enables the optical head 14 toreproduce management information from the management area 13 c of theoptical disc 13F. The system controller 22F detects the conditions ofthe unoccupied regions in the first and second areas 13 a and 13 b ofthe optical disc 13F by referring to the reproduced managementinformation. The system controller 22F decides whether or not thecontinuously and simultaneously recording of the contents of the firstand second information signals “A” and “B” can be implemented on thebasis of the detected conditions of the unoccupied regions and thepreviously-indicated relation (9) or (19). When the system controller22F decides that the continuously and simultaneously recording of thecontents of the first and second information signals “A” and “B” can beimplemented, the actually recording of the information signals “A” and“B” on the optical disc 13F is started.

[0415] During a recording/playback mode of operation of the apparatus10F, the optical head 14 reproduces a first information signal “A” fromthe first areas 13 a in the optical disc 13F. The first informationsignal “A” is stored into the first area 19 a in the track buffer memory19 from the optical head 14 at the predetermined constant transfer rateRp. The first information signal “A” is transmitted from the trackbuffer memory 19 to the audio-video encoding and decoding unit 20 at thetransfer rate Ra. On the other hand, a second information signal “B” isinputted into the second area 19 b in the track buffer memory 19 at thetransfer rate Rb. The second information signal “B” is transmitted fromthe track buffer memory 19 to the optical head 14 at the predeterminedconstant transfer rate Rp. The optical head 14 records the secondinformation signal “B” on unoccupied regions in the second areas 13 b ofthe optical disc 13F. The optical head 14 implements the reproduction ofthe first information signal “A” and the recording of the secondinformation signal “B” on a time sharing basis. At an initial stage ofthe recording/playback mode of operation, the system controller 22Fenables the optical head 14 to reproduce management information from themanagement area 13 c of the optical disc 13F. The system controller 22Fdetects the conditions of the unoccupied regions in the second areas 13b of the optical disc 13F by referring to the reproduced managementinformation. The system controller 22F decides whether or not theplayback of the contents of the first information signal “A” and therecording of the contents of the second information signal “B” can becontinuously and simultaneously implemented on the basis of the detectedconditions of the unoccupied regions and the previously-indicatedrelation (9) or (19). When the system controller 22F decides that theplayback of the contents of the first information signal “A” and therecording of the contents of the second information signal “B” can becontinuously and simultaneously implemented, the actually playback ofthe first information signal “A” and the actually recording of thesecond information signal “B” are started.

[0416] For example, the system controller 22F executes the calculationsand the decisions regarding the relation (9) or (19) each time therecording mode of operation or the recording/playback mode of operationis implemented. The program ROM in the system controller 22F may store atable of the results of previously-executed calculations of the relation(9) or (19). In this case, the table is accessed when the conditionsdetermined by the relation (9) or (19) are required to be detected.

[0417] When the sum of the transfer rates Ra and Rb for the first andsecond information signals “A” and “B” is greater than the predeterminedconstant transfer rate Rp in the relation (9) or (19), it is difficultto implement the continuously and simultaneously recording of thecontents of the first and second information signals “A” and “B”. Inaddition, it is difficult to continuously and simultaneously implementthe playback of the contents of the first information signal “A” and therecording of the contents of the second information signal “B”. In thesecases, the system controller 22F controls the display 225 via theaudio-video encoding and decoding unit 20 and the NTSC encoder 224 toindicate the related difficulty.

[0418] Regarding the recording of the first and second informationsignals “A” and “B”, the system controller 22F executes the followingcalculations for each of the first and second information signals “A”and “B”. Specifically, the system controller 22F calculates the totalsize of the unoccupied regions in the optical disc 13F. For each of the2-Mbps, 4-Mbps, 8-Mbps, and 17-Mbps transfer rates, the systemcontroller 22F calculates the recording time (or the recordingcapacity). For each of the 2-Mbps, 4-Mbps, 8-Mbps, and 17-Mbps transferrates, the system controller 22F calculates the total size of usableportions of the unoccupied regions in the optical disc 13F. For each ofthe 2-Mbps, 4-Mbps, 8-Mbps, and 17-Mbps transfer rates, the systemcontroller 22F calculates the region use efficiency (%) which is equalto the ratio between the total size of the unoccupied regions and thetotal size of usable portions of the unoccupied regions in the opticaldisc 13F. The system controller 22F controls the display 225 via theaudio-video encoding and decoding unit 20 and the NTSC encoder 224 toindicate the calculated total size of the unoccupied regions in theoptical disc 13F, the calculated recording times, the calculated totalsizes of usable portions of the unoccupied regions in the optical disc13F, and the calculated region use efficiencies. An example of thisindication is shown in FIG. 34 where only the calculated items availableat a transfer rate Ra of 8 Mbps are displayed. In the case where Ra=8Mbps and Rb=17 Mbps, neither the relation (9) nor the relation (19) issatisfied so that the continuously and simultaneously recording of thecontents of the first and second information signals “A” and “B” isdifficult or impossible. In this case, the system controller 22Fcontrols the display 225 via the audio-video encoding and decoding unit20 and the NTSC encoder 224 to indicate “recording impossible” as shownin FIG. 34.

[0419] Regarding the playback of the first information signal “A” andthe recording of the second information signal “B”, the systemcontroller 22F calculates the total size of the unoccupied regions inthe second areas 13 b of the optical disc 13F. For each of the 2-Mbps,4-Mbps, 8-Mbps, and 17-Mbps transfer rates, the system controller 22Fcalculates the recording time (or the recording capacity). For each ofthe 2-Mbps, 4-Mbps, 8-Mbps, and 17-Mbps transfer rates, the systemcontroller 22F calculates the total size of usable portions of theunoccupied regions in the second areas 13 b of the optical disc 13F. Foreach of the 2-Mbps, 4-Mbps, 8-Mbps, and 17-Mbps transfer rates, thesystem controller 22F calculates the region use efficiency (%) which isequal to the ratio between the total size of the unoccupied regions andthe total size of usable portions of the unoccupied regions in theoptical disc 13F. The system controller 22F controls the display 225 viathe audio-video encoding and decoding unit 20 and the NTSC encoder 224to indicate the calculated total size of the, unoccupied regions in theoptical disc 13F, the calculated recording times, the calculated totalsizes of usable portions of the unoccupied regions in the optical disc13F, and the calculated region use efficiencies. An example of thisindication is shown in FIG. 35 where only the calculated items availableat a transfer rate Ra of 8 Mbps are displayed. In the-case where Ra=8Mbps and Rb=17 Mbps, neither the relation (9) nor the relation (19) issatisfied so that it is difficult to continuously and simultaneouslyimplement the playback of the contents of the first information signal“A” and the recording of the contents of the second information signal“B”. In this case, the system controller 22F controls the display 225via the audio-video encoding and decoding unit 20 and the NTSC encoder224 to indicate “recording impossible” as shown in FIG. 35.

[0420] The on-display indications in FIGS. 33, 34, and 35 may bemodified as follows. The calculated total sizes of usable portions ofthe unoccupied regions in the optical disc 13F may be omitted from theindications. The transfer rates may be replaced by “high picturequality”, “slightly high picture quality”, and “normal picture quality”.The transfer rates may be replaced by “2-hour recording mode”, “4-hourrecording mode”, and “8-hour recording mode”.

[0421] Generally, the user operates a key input unit 23 and therebyselects the desired values of the transfer rates Ra and Rb inconsideration of the items indicated on the display 225. During a laterstage of operation of the apparatus 10F, the actual values of thetransfer rates Ra and Rb are equalized to the desired values thereof. Inthe absence of user's selection of the transfer rates Ra and Rb, thehighest values of the transfer rates Ra and Rb are automatically set asthe desired values thereof.

[0422] Two-Signal Recording Mode

[0423] The system controller 22F operates in accordance with a programstored in its internal ROM. FIG. 36 is a flowchart of a segment of theprogram which relates to a two-signal recording mode of operation of theapparatus 10F. The program segment in FIG. 36 is started in response toa two-signal-recording start command signal fed from the key input unit23. In this case, the optical disc 13F is of the rewritable type.

[0424] With reference to FIG. 36, a first step S252 of the programsegment controls the optical head 14 to reproduce management informationfrom the management area 13 c in the optical disc 13F.

[0425] A step S253 following the step S252 searches for unoccupiedregions in the first and second areas 13 a and 13 b of the optical disc13F by referring to address information contained in the reproducedmanagement information. The step S253 decides whether or not thecontinuously and simultaneously recording of the contents of first andsecond information signals “A” and “B” can be implemented on the basisof the conditions of the unoccupied regions and the previously-indicatedrelation (9) or (19). The step S253 indicates the result of the decisionon the display 225. When it is decided that the continuously andsimultaneously recording of the contents of the first and secondinformation signals “A” and “B” can be implemented, the program advancesfrom the step S253 to a step S254.

[0426] The step S254 decides whether or not the optical head 14 hasreached a target position on the optical disc 13F. Initially, the targetposition corresponds to first one A1 of the first areas 13 a in theoptical disc 13F. When the optical head 14 has not reached the targetposition yet, the step S254 is repeated. When the optical head 14 hasreached the target position, the program advances from the step S254 toa step S255.

[0427] The step S255 stores the first information signal “A”, which isoutputted from the audio-video encoding and decoding unit 20, into thefirst area 19 a in the track buffer memory 19 at the transfer rate Ra.

[0428] A step S256 following the step S255 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related full value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S256 to thestep S255. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S256 to a step S257.

[0429] The step S257 transfers the first information signal “A” from thefirst area 19 a in the track buffer memory 19 to the optical head 14 atthe predetermined constant transfer rate Rp. The step S257 enables theoptical head 14 to record the first information signal “A” on thepresent first area 13 a in the optical disc 13F at the predeterminedconstant transfer rate Rp.

[0430] A step S258 following the step S257 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related empty value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S258 to thestep S257. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S258 to a step S259.

[0431] The step S259 forces the optical head 14 to suspend the recordingof the first information signal “A” on the present first area 13 a inthe optical disc 13F.

[0432] A step S260 subsequent to the step S259 moves the optical head 14toward a next target position. The next target position corresponds to,for example, first one BI of the second areas 13 b in the optical disc13F. After the step S260, the program advances to a step S261.

[0433] The step S261 decides whether or not the optical head 14 hasreached the target position on the optical disc 13F. When the opticalhead 14 has not reached the target position yet, the step S261 isrepeated. When the optical head 14 has reached the target position, theprogram advances from the step S261 to a step S262.

[0434] In this way, the optical head 14 moves from the first area 13 ato the second area 13 b in the optical disc 13F. The seek time Tabrelated to this movement of the optical head 14 is equal to 1.5 secondsor shorter.

[0435] The step S262 stores the second information signal “B”, which isoutputted from the audio-video encoding and decoding unit 20, into thesecond area 19 b in the track buffer memory 19 at the transfer rate Rb.

[0436] A step S263 following the step S262 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related full value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S263 to thestep S262. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S263 to a step S264.

[0437] The step S264 transfers the second information signal “B” fromthe second area 19 b in the track buffer memory 19 to the optical head14 at the predetermined constant transfer rate Rp. The step S264 enablesthe optical head 14 to record the second information signal “B” on thepresent second area 13 b in the optical disc 13F at the predeterminedconstant transfer rate Rp.

[0438] A step S265 following the step S264 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related empty value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S265 to thestep S264. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S265 to a step S266.

[0439] The step S266 forces the optical head 14 to suspend the recordingof the second information signal “B” on the present second area 13 b inthe optical disc 13F.

[0440] A step S267 subsequent to the step S266 moves the optical head 14toward a next target position. The next target position corresponds to,for example, second one A2 of the first areas 13 a in the optical disc13F. After the step S267, the program returns to the step S254.

[0441] Thus, the optical head 14 moves from the second area 13 b to thefirst area 13 a in the optical disc 13F. The seek time Tba related tothis movement of the optical head 14 is equal to 1.5 seconds or shorter.

[0442] During the repetitive execution of the program segment in FIG.36, the target position of the optical head 14 is sequentially set intocorrespondence with the first and second areas A1, B1, A2, B2, A3, B3, .. . in the optical disc 13F. Therefore, the optical head 14 alternatelyrecords the first information signal “A” and the second informationsignal “B” on the first and second areas 13 a and 13 b of the opticaldisc 13 in the order as “A1, B1, A2, B2, A3, B3, . . . ”.

[0443] Preferably, the step S259 or the step S266 is followed by a stepwhich decides whether or not both the recording of the first informationsignal “A” on the optical disc 13F and the recording of the secondinformation signal “B” thereon are required to be suspended. In thiscase, when both the recording of the first information signal “A” on theoptical disc 13F and the recording of the second information signal “B”thereon are required to be suspended, the optical head 14 is controlledto implement the required suspension of recording.

[0444] After the recording of the first and second information signals“A” and “B” on the optical disc 13F has been completed, informationrepresenting the addresses of the first and second information signals“A” and “B” on the optical disc 13F is recorded on the management area13 c of the optical disc 13F. In addition, information representing thetransfer rates Ra and Rb for the first and second information signals“A” and “B” may be recorded on the management area 13 c of the opticaldisc 13F.

[0445] Signal Recording/Playback Mode

[0446] The system controller 22F operates in accordance with the programstored in its internal ROM. FIG. 37 is a flowchart of a segment of theprogram which relates to a signal recording/playback mode of operationof the apparatus 10F. The program segment in FIG. 37 is started inresponse to a signal-recording/playback start command signal fed fromthe key input unit 23. In this case, the optical disc 13F is of therewritable type.

[0447] With reference to FIG. 37, a first step S272 of the programsegment controls the optical head 14 to reproduce management informationfrom the management area 13 c in the optical disc 13F.

[0448] A step S273 extracts the positional information and the playbackinformation related to a first information signal “A” from thereproduced management information. The playback information containsinformation representing the transfer rate Ra for the first informationsignal “A”. In addition, the step S273 searches for unoccupied regionsin the second areas 13 b of the optical disc 13F by referring to addressinformation contained in the reproduced management information. The stepS273 decides whether or not the playback of the contents of the firstinformation signal “A” and the recording of the contents of a secondinformation signal “B” can be continuously and simultaneouslyimplemented on the basis of the conditions of the unoccupied regions andthe previously-indicated relation (9) or (19). The step S273 indicatesthe result of the decision on the display 225. When it is decided thatthe playback of the contents of the first information signal “A” and therecording of the contents of the second information signal “B” can becontinuously and simultaneously implemented, the program advances fromthe step S273 to a step S274.

[0449] The step S274 decides whether or not the optical head 14 hasreached a target position on the optical disc 13F. Initially, the targetposition corresponds to first one A1 of the first areas 13 a in theoptical disc 13F. When the optical head 14 has not reached the targetposition yet, the step S274 is repeated. When the optical head 14 hasreached the target position, the program advances from the step S274 toa step S275.

[0450] The step S275 enables the optical head 14 to reproduce the firstinformation signal “A” from the present first area 13 a in the opticaldisc 13F. The step S275 stores the reproduced first information signal“A” into the first area 19 a in the track buffer memory 19 at thepredetermined constant transfer rate Rp.

[0451] A step S276 following the step S275 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related empty value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S276 to thestep S275. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S276 to a step S277.

[0452] The step S277 transfers the first information signal “A” from thefirst area 19 a in the track buffer memory 19 to the audio-videoencoding and decoding unit 20 at the transfer rate Ra.

[0453] A step S278 following the step S277 decides whether or not thedegree of occupancy of the first area 19 a in the track buffer memory 19has reached the related full value. When the degree of occupancy of thefirst area 19 a in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S278 to thestep S277. When the degree of occupancy of the first area 19 a in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S278 to a step S279.

[0454] The step S279 forces the optical head 14 to suspend thereproduction of the first information signal “A” from the present firstarea 13 a in the optical disc 13F.

[0455] A step S280 subsequent to the step S279 moves the optical head 14toward a next target position. The next target position corresponds to,for example, first one B1 of the second areas 13 b in the optical disc13F. After the step S280, the program advances to a step S281.

[0456] The step S281 decides whether or not the optical head 14 hasreached the target position on the optical disc 13F. When the opticalhead 14 has not reached the target position yet, the step S281 isrepeated. When the optical head 14 has reached the target position, theprogram advances from the step S281 to a step S282.

[0457] In this way, the optical head 14 moves from the first area 13 ato the second area 13 b. The seek time Tab related to this movement ofthe optical head 14 is equal to 1.5 seconds or shorter.

[0458] The step S282 stores the second information signal “B”, which isoutputted from the audio-video encoding and decoding unit 20, into thesecond area 19 b in the track buffer memory 19 at the transfer rate Rb.

[0459] A step S283 following the step S282 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related full value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated full value yet, the program returns from the step S283 to thestep S282. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related full value, the programadvances from the step S283 to a step S284.

[0460] The step S284 transfers the second information signal “B” fromthe second area 19 b in the track buffer memory 19 to the optical head14 at the predetermined constant transfer rate Rp. The step S284 enablesthe optical head 14 to record the second information signal “B” on thepresent second area 13 b in the optical disc 13 at the predeterminedconstant transfer rate Rp.

[0461] A step S285 following the step S284 decides whether or not thedegree of occupancy of the second area 19 b in the track buffer memory19 has reached the related empty value. When the degree of occupancy ofthe second area 19 b in the track buffer memory 19 has not reached therelated empty value yet, the program returns from the step S285 to thestep S284. When the degree of occupancy of the second area 19 b in thetrack buffer memory 19 has reached the related empty value, the programadvances from the step S285 to a step S286.

[0462] The step S286 forces the optical head 14 to suspend the recordingof the second information signal “B” on the present second area 13 b inthe optical disc 13F.

[0463] A step S287 subsequent to the step S286 moves the optical head 14toward a next target position. The next target position corresponds to,for example, second one A2 of the first areas 13 a in the optical disc13F. After the step S287, the program returns to the step S274.

[0464] Thus, the optical head 14 moves from the second area 13 b to thefirst area 13 a. The seek time Tba related to this movement of theoptical head 14 is equal to 1.5 seconds or shorter.

[0465] During the repetitive execution of the program segment in FIG.37, the target position of the optical head 14 is sequentially set intocorrespondence with the first and second areas A1, B1, A2, B2, A3, B3, .. . in the optical disc 13F. Therefore, the optical head 14 alternatelyreproduces the first information signal “A” and records the secondinformation signal “B” while accessing the first and second areas 13 aand 13 b of the optical disc 13 in the order as “A1, B1, A2, B2, A3, B3,. . . ”.

[0466] Preferably, the step S279 or the step S286 is followed by a stepwhich decides whether or not both the reproduction of the firstinformation signal “A” from the optical disc 13F and the recording ofthe second information signal “B” thereon are required to be suspended.In this case, when both the reproduction of the first information signal“A” from the optical disc 13F and the recording of the secondinformation signal “B” thereon are required to be suspended, the opticalhead 14 is controlled to implement the required suspension ofreproduction and recording.

[0467] After the playback of the first information signal “A” from theoptical disc 13F and the recording of the second information signal “B”thereon have been completed, information representing the addresses ofthe second information signal “B” on the optical disc 13F is recorded onthe management area 13 c of the optical disc 13F. In addition,information representing the transfer rate Rb for the second informationsignal “B” may be recorded on the management area 13 c of the opticaldisc 13F.

Other Features and Aspects of Embodiments

[0468] According to the basic aspects of the previously-mentionedembodiments of this invention, the signal transfer rate related to therecording and reproduction of information on and from a recording mediumis fixed to the predetermined constant transfer rate Rp.

[0469] Generally, the previously-mentioned embodiments of this inventioncan operate on a recording medium such as a DVD-ROM, a DVD-RW, aDVD-RAM, a DVD+RW, and an HDD magnetic disc.

[0470] A DVD-ROM or a DVD-RW is subjected to CLV (constant linearvelocity) control by a disc drive. Thus, the signal transfer rate isfixed throughout the whole area of the DVD-ROM or the DVD-RW.

[0471] A DVD-RAM is divided into zones. The DVD-RAM is subjected to zoneCLV by a disc drive. The signal transfer rate varies from zone to zoneby only several percent. The previously-mentioned embodiments of thisinvention arc adaptable to such a slightly-varying signal transfer rate.

[0472] Regarding a DVD+RW or an HDD magnetic disc, the signal transferrate sometimes depends on a disc radial position. Thepreviously-mentioned embodiments of this invention can be applied to adisc area in which the signal transfer rate varies by several percent toseveral tens of percent.

[0473] In these case, it is preferable to calculate the signal transferrate (Rp) regarding a recording medium as a minimum signal transfer ratewhich occurs when recording or reproduction is performed.

[0474] According to the previously-mentioned embodiments of thisinvention, information is recorded on and reproduced from two or moreareas of a recording medium. The two or more areas of the recordingmedium may be a common area. In this case, the previously-mentionedembodiments of this invention are designed to operate in one of thefollowing modes. During a first mode of operation, first data arereproduced from an area of a recording medium and a portion of thereproduced first data is changed to form second data, and the seconddata are recorded on the same area of the recording medium. During asecond mode of operation, data are recorded on an area of a recordingmedium, and then the data are reproduced therefrom and the reproduceddata are analyzed to verify whether the data have been correctlyrecorded on the area of the recording medium.

[0475] In the previous description of the embodiments of this invention,“seek time” taken by the optical head to move from a first disc positionto a second disc position is generally equal to a time for radial headmovement from a first track (a first track portion) having the firstdisc position to a second track (a second track portion) having thesecond disc position plus a rotation waiting time for which the opticalhead remains on or above the second track (the second track portion)until meeting the second disc position. In the case where the first andsecond tracks (the first and second track portions) neighbor each other,“seek time” is equal to only a rotation waiting time.

What is claimed is:
 1. An apparatus for reproducing information from arecording medium having first and second areas on which first and secondinformation signals are recorded respectively, the first informationsignal having a size Ya, the second information signal having a size Yb,the apparatus comprising: a head for reproducing the first and secondinformation signals from the first and second areas of the recordingmedium and transmitting the reproduced first and second informationsignals on a time sharing basis and at a predetermined constant transferrate Rp while moving between the first and second areas of the recordingmedium; and a buffer memory for receiving the first and secondinformation signals from the head at the predetermined constant transferrate Rp, for temporarily storing the first and second informationsignals, and for outputting the first and second information signals atfirst and second transfer rates Ra and Rb respectively, the first andsecond transfer rates Ra and Rb being lower than the predeterminedconstant transfer rate Rp; wherein the predetermined constant transferrate Rp, the first transfer rate Ra for the first information signal,the second transfer rate Rb for the second information signal, the sizeYa of the first information signal, the size Yb of the secondinformation signal, a seek time Tab taken by the head to move from thefirst area to the second area of the recording medium, and a seek timeTba taken by the head to move from the second area to the first area ofthe recording medium are in a relation as follows:(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)
 2. An apparatus for recordinginformation on a recording medium having first and second areas, theapparatus comprising: a buffer memory for receiving first and secondinformation signals at first and second transfer rates Ra and Rbrespectively, for temporarily storing the first and second informationsignals, and for outputting the first and second information signals ata predetermined constant transfer rate Rp higher than the first andsecond transfer rates Ra and Rb, the first information signal having asize Ya, the second information signal having a size Yb; and a head forreceiving the first and second information signals from the buffermemory, and for recording the first and second information signals onthe first and second areas of the recording medium respectively on atime sharing basis and at the predetermined constant transfer rate Rpwhile moving between the first and second areas of the recording medium;wherein the predetermined constant transfer rate Rp, the first transferrate Ra for the first information signal, the second transfer rate Rbfor the second information signal, the size Ya of the first informationsignal, the size Yb of the second information signal, a seek time Tabtaken by the head to move from the first area to the second area of therecording medium, and a seek time Tba taken by the head to move from thesecond area to the first area of the recording medium are in a relationas follows: (Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)
 3. An apparatus forrecording and reproducing information on and from a recording mediumhaving first and second areas, the first area being loaded with a firstinformation signal having a size Ya, the apparatus comprising: a headfor reproducing the first information signal from the first area of therecording medium and transmitting the reproduced first informationsignal at a predetermined constant transfer rate Rp; and a buffer memoryfor receiving the first information signal from the head at thepredetermined constant transfer rate Rp, for temporarily storing thefirst information signal, and for outputting the first informationsignal at a first transfer rate Ra lower than the predetermined constanttransfer rate Rp; the buffer memory being for receiving a secondinformation signal at a second transfer rate Rb lower than thepredetermined constant transfer rate Rp, for temporarily storing thesecond information signal, and for outputting the second informationsignal at the predetermined constant transfer rate Rp, the secondinformation signal having a size Yb; the head being for receiving thesecond information signal from the buffer memory, and for recording thesecond information signal on the second area of the recording medium atthe predetermined constant transfer rate Rp; wherein the head implementsreproduction of the first information signal from the first area of therecording medium and recording of the second information signal on thesecond area of the recording medium on a time sharing basis while movingbetween the first and second areas of the recording medium; and whereinthe predetermined constant transfer rate Rp, the first transfer rate Rafor the first information signal, the second transfer rate Rb for thesecond information signal, the size Ya of the first information signal,the size Yb of the second information signal, a seek time Tab taken bythe head to move from the first area to the second area of the recordingmedium, and a seek time Tba taken by the head to move from the secondarea to the first area of the recording medium are in a relation asfollows: (Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)
 4. An apparatus forreproducing information from a recording medium having first and secondareas on which first and second information signals are recordedrespectively, the apparatus comprising: a head for reproducing the firstand second information signals from the first and second areas of therecording medium and transmitting the reproduced first and secondinformation signals on a time sharing basis and at a predeterminedconstant transfer rate Rp while moving between the first and secondareas of the recording medium; and a buffer memory for receiving thefirst and second information signals from the head at the predeterminedconstant transfer rate Rp, for temporarily storing the first and secondinformation signals, and for outputting the first and second informationsignals at first and second transfer rates Ra and Rb respectively, thefirst and second transfer rates Ra and Rb being lower than thepredetermined constant transfer rate Rp, the buffer memory having acapacity Ym; wherein the predetermined constant transfer rate Rp, thefirst transfer rate Ra for the first information signal, the secondtransfer rate Rb for the second information signal, the capacity Ym ofthe buffer memory, a seek time Tab taken by the head to move from thefirst area to the second area of the recording medium, and a seek timeTba taken by the head to move from the second area to the first area ofthe recording medium are in a relation as follows:Ym>{(Rp−Ra)·Ra+(Rp−Rb)·Rb}·(Tab+Tba)/(Rp−Ra−Rb)
 5. An apparatus forrecording information on a recording medium having first and secondareas, the apparatus comprising: a buffer memory for receiving first andsecond information signals at first and second transfer rates Ra and Rbrespectively, for temporarily storing the first and second informationsignals, and for outputting the first and second information signals ata predetermined constant transfer rate Rp higher than the first andsecond transfer rates Ra and Rb, the buffer memory having a capacity Ym;and a head for receiving the first and second information signals fromthe buffer memory, and for recording the first and second informationsignals on the first and second areas of the recording mediumrespectively on a time sharing basis and at the predetermined constanttransfer rate Rp while moving between the first and second areas of therecording medium; wherein the predetermined constant transfer rate Rp,the first transfer rate Ra for the first information signal, the secondtransfer rate Rb for the second information signal, the capacity Ym ofthe buffer memory, a seek time Tab taken by the head to move from thefirst area to the second area of the recording medium, and a seek timeTba taken by the head to move from the second area to the first area ofthe recording medium are in a relation as follows:Ym>{(Rp−Ra)·Ra+(Rp−Rb)·Rb}·(Tab+Tba)/(Rp−Ra−Rb)
 6. An apparatus forrecording and reproducing information on and from a recording mediumhaving first and second areas, the first area being loaded with a firstinformation signal, the apparatus comprising: a head for reproducing thefirst information signal from the first area of the recording medium andtransmitting the reproduced first information signal at a predeterminedconstant transfer rate, Rp; and a buffer memory for receiving the firstinformation signal from the head at the predetermined constant transferrate Rp, for temporarily storing the first information signal, and foroutputting the first information signal at a first transfer rate Ralower than the predetermined constant transfer rate Rp, the buffermemory having a capacity Ym; the buffer memory being for receiving asecond information signal at a second transfer rate Rb lower than thepredetermined constant transfer rate Rp, for temporarily storing thesecond information signal, and for outputting the second informationsignal at the predetermined constant transfer rate Rp; the head beingfor receiving the second information signal from the buffer memory, andfor recording the second information signal on the second area of therecording medium at the predetermined constant transfer rate Rp; whereinthe head implements reproduction of the first information signal fromthe first area of the recording medium and recording of the secondinformation signal on the second area of the recording medium on a timesharing basis while moving between the first and second areas of therecording medium; and wherein the predetermined constant transfer rateRp, the first transfer rate Ra for the first information signal, thesecond transfer rate Rb for the second information signal, the capacityYm of the buffer memory, a seek time Tab taken by the head to move fromthe first area to the second area of the recording medium, and a seektime Tba taken by the head to move from the second area to the firstarea of the recording medium are in a relation as follows:Ym>{(Rp−Ra)·Ra+(Rp−Rb)·Rb}·(Tab+Tba)/(Rp−Ra−Rb)
 7. An apparatus asrecited in claim 1, further comprising means for partitioning the buffermemory into first and second areas in accordance with values of thefirst and second transfer rates Ra and Rb, wherein the first and secondareas in the buffer memory are assigned to the first and secondinformation signals respectively.
 8. An apparatus as recited in claim 1,further comprising means for partitioning the buffer memory into firstand second areas in accordance with an operation mode, wherein the firstand second areas in the buffer memory are assigned to the first andsecond information signals respectively.
 9. An apparatus as recited inclaim 1, further comprising a first unit containing the head, and asecond unit detachably connected with the first unit and containing thebuffer memory.
 10. An apparatus comprising: a head for reproducing aninformation signal from a recording medium and transmitting thereproduced information signal at a predetermined constant transfer rate;a buffer memory for receiving the information signal from the head atthe predetermined constant transfer rate, for temporarily storing theinformation signal, and for outputting the information signal at atransfer rate lower than the predetermined constant transfer rate; aprocessor for receiving the information signal from the buffer memoryand subjecting the information signal to a reproducing process; a firstunit containing the head; and a second unit detachably connected withthe first unit and containing the buffer memory and the processor. 11.An information-signal communication apparatus comprising the apparatusof claim 1 and an interface connected with the buffer memory forcommunication with an external.
 12. An information-signal communicationapparatus as recited in claim 11, further comprising a first unitcontaining the head, and a second unit detachably connected with thefirst unit and the interface and containing the buffer memory.
 13. Aninformation-signal recording medium having first and second areas onwhich first and second information signals are recorded respectively,the first information signal having a size Ya, the second informationsignal having a size Yb, wherein the first and second informationsignals can be reproduced from the first and second areas and can betransmitted by a head on a time sharing basis and at a predeterminedconstant transfer rate Rp while the head moves between the first andsecond areas of the recording medium, wherein the first and secondinformation signals outputted from the head can be received by a buffermemory at the predetermined constant transfer rate Rp and can betemporarily stored in the buffer memory before being outputted from thebuffer memory at first and second transfer rates Ra and Rb respectively,the first and second transfer rates Ra and Rb being lower than thepredetermined constant transfer rate Rp, wherein the predeterminedconstant transfer rate Rp, the first transfer rate Ra for the firstinformation signal, the second transfer rate Rb for the secondinformation signal, the size Ya of the first information signal, thesize Yb of the second information signal, a seek time Tab taken by thehead to move from the first area to the second area of the recordingmedium, and a seek time Tba taken by the head to move from the secondarea to the first area of the recording medium are in a relation asfollows: (Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)
 14. An apparatus forreproducing information from a recording medium having “n” areas onwhich “n” information signals are recorded respectively, where “n”denotes a predetermined natural number equal to or greater than 2, theapparatus comprising: a head for reproducing the “n” information signalsfrom the “n” areas of the recording medium and transmitting thereproduced “n” information signals on a time sharing basis and at apredetermined constant transfer rate Rp while moving among the “n” areasof the recording medium; and a buffer memory for receiving the “n”information signals from the head at the predetermined constant transferrate Rp, for temporarily storing the “n” information signals, and foroutputting the “n” information signals at transfer rates R1, R2, . . . ,Rn respectively, the transfer rates R1, R2, . . . , Rn being lower thanthe predetermined constant transfer rate Rp; wherein the predeterminedconstant transfer rate Rp, a sum ΣRn of the transfer rates R1, R2, . . ., Rn, a sum ΣYn of sizes of the “n” information signals, and a sum ΣSnof seek times taken by the head to move from present ones to next onesof the “n” areas of the recording medium are in a relation as follows:ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)
 15. An apparatus for recording information on arecording medium having “n” areas, where “n” denotes a predeterminednatural number equal to or greater than 2, the apparatus comprising: abuffer memory for receiving “n” information signals at transfer ratesR1, R2, . . . , Rn respectively, for temporarily storing the “n”information signals, and for outputting the “n” information signals at apredetermined constant transfer rate Rp higher than the transfer ratesR1, R2, . . . , Rn; and a head for receiving the “n” information signalsfrom the buffer memory, and for recording the “n” information signals onthe “n” areas of the recording medium respectively on a time sharingbasis and at the predetermined constant transfer rate Rp while movingamong the “n” areas of the recording medium; wherein the predeterminedconstant transfer rate Rp, a sum ΣRn of the transfer rates R1, R2, . . ., Rn, a sum ΣYn of sizes of the “n” information signals, and a sum ΣSnof seek times taken by the head to move from present ones to next onesof the “n” areas of the recording medium are in a relation as follows:ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)
 16. An apparatus for recording and reproducinginformation on and from a recording medium having “n” areas, where “n”denotes a predetermined natural number equal to or greater than 2,wherein at least a first area among the “n” areas is loaded with a firstinformation signal among “n” information signals, the apparatuscomprising: a head for reproducing the first information signal from thefirst area of the recording medium and transmitting the reproduced firstinformation signal at a predetermined constant transfer rate Rp; and abuffer memory for receiving the first information signal from the headat the predetermined constant transfer rate Rp, for temporarily storingthe first information signal, and for outputting the first informationsignal at a first transfer rate R1 lower than the predetermined constanttransfer rate Rp; the buffer memory being for receiving the “n”information signals except the first information signal at transferrates R2, R3, . . . , Rn respectively, for temporarily storing the “n”information signals except the first information signal, and foroutputting the “n” information signals except the first informationsignal at the predetermined constant transfer rate Rp, the transferrates R2, R3, . . . , Rn being lower than the predetermined constanttransfer rate Rp; the head being for receiving the “n” informationsignals except the first information signal from the buffer memory, andfor recording the “n” information signals except the first informationsignal on the “n” areas of the recording medium except the first area atthe predetermined constant transfer rate Rp; wherein the head implementsreproduction of the first information signal from the first area of therecording medium and recording of the “n” information signals except thefirst information signal on the “n” areas of the recording medium exceptthe first area on a time sharing basis while moving among the “n” areasof the recording medium; and wherein the predetermined constant transferrate Rp, a sum ΣRn of the transfer rates R1, R2, . . . , Rn, a sum ΣYnof sizes of the “n” information signals, and a sum ΣSn of seek timestaken by the head to move from present ones to next ones of the “n”areas of the recording medium are in a relation as follows:ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)
 17. An apparatus for reproducing informationfrom a recording medium having “n” areas on which “n” informationsignals are recorded respectively, where “n” denotes a predeterminednatural number equal to or greater than 2, the apparatus comprising: ahead for reproducing the “n” information signals from the “n” areas ofthe recording medium and transmitting the reproduced “n” informationsignals on a time sharing basis and at a predetermined constant transferrate Rp while moving among the “n” areas of the recording medium; and abuffer memory for receiving the “n” information signals from the head atthe predetermined constant transfer rate Rp, for temporarily storing the“n” information signals, and for outputting the “n” information signalsat transfer rates R1, R2, . . . , Rn respectively, the transfer ratesR1, R2, . . . , Rn being lower than the predetermined constant transferrate Rp; wherein the predetermined constant transfer rate Rp, a sum ΣRnof the transfer rates R1, R2, . . . , Rn, a sum ΣYn of sizes of the “n”information signals, and an allowable seek time S taken by the head tomove from present one to next one of the “n” areas of the recordingmedium are in a relation as follows: ΣYn≧Rp·ΣRn·n·S/(Rp−ΣRn)
 18. Anapparatus for recording information on a recording medium having “n”areas, where “n” denotes a predetermined natural number equal to orgreater than 2, the apparatus comprising: a buffer memory for receiving“n” information signals at transfer rates R1, R2, . . . , Rnrespectively, for temporarily storing the “n” information signals, andfor outputting the “n” information signals at a predetermined constanttransfer rate Rp higher than the transfer rates R1, R2, . . . , Rn; anda head for receiving the “n” information signals from the buffer memory,and for recording the “n” information signals on the “n” areas of therecording medium respectively on a time sharing basis and at thepredetermined constant transfer rate Rp while moving among the “n” areasof the recording medium; wherein the predetermined constant transferrate Rp, a sum ΣRn of the transfer rates R1, R2, . . . , Rn, a sum ΣYnof sizes of the “n” information signals, and an allowable seek time Staken by the head to move from present one to next one of the “n” areasof the recording medium are in a relation as follows:ΣYn≧Rp·ΣRn·n·S/(Rp−ΣRn)
 19. An apparatus for recording and reproducinginformation on and from a recording medium having “n” areas, where “n”denotes a predetermined natural number equal to or greater than 2,wherein at least a first area among the “n” areas is loaded with a firstinformation signal among “n” information signals, the apparatuscomprising: a head for reproducing the first information signal from thefirst area of the recording medium and transmitting the reproduced firstinformation signal at a predetermined constant transfer rate Rp; and abuffer memory for receiving the first information signal from the headat the predetermined constant transfer rate Rp, for temporarily storingthe first information signal, and for outputting the first informationsignal at a first transfer rate R1 lower than the predetermined constanttransfer rate Rp; the buffer memory being for receiving the “n”information signals except the first information signal at transferrates R2, R3, . . . , Rn respectively, for temporarily storing the “n”information signals except the first information signal, and foroutputting the “n” information signals except the first informationsignal at the predetermined constant transfer rate Rp, the transferrates R2, R3, . . . , Rn being lower than the predetermined constanttransfer rate Rp; the head being for receiving the “n” informationsignals except the first information signal from the buffer memory, andfor recording the “n” information signals except the first informationsignal on the “n” areas of the recording medium except the first area atthe predetermined constant transfer rate Rp; wherein the head implementsreproduction of the first information signal from the first area of therecording medium and recording of the “n” information signals except thefirst information signal on the “n” areas of the recording medium exceptthe first area on a time sharing basis while moving among the “n” areasof the recording medium; and wherein the predetermined constant transferrate Rp, a sum ΣRn of the transfer rates R1, R2, . . . , Rn, a sum ΣYnof sizes of the “n” information signals, and an allowable seek time Staken by the head to move from present one to next one of the “n” areasof the recording medium are in a relation as follows:ΣYn≧Rp·ΣRn·n·S/(Rp−ΣRn)
 20. An apparatus for reproducing informationfrom a recording medium having “n” areas on which “n” informationsignals are recorded respectively, where “n” denotes a predeterminednatural number equal to or greater than 2, the apparatus comprising: ahead for reproducing the “n” information signals from the “n” areas ofthe recording medium and transmitting the reproduced “n” informationsignals on a time sharing basis and at a predetermined constant transferrate Rp while moving among the “n” areas of the recording medium; and abuffer memory for receiving the “n” information signals from the head atthe predetermined constant transfer rate Rp, for temporarily storing the“n” information signals, and for outputting the “n” information signalsat transfer rates R1, R2, . . . , Rn respectively, the transfer ratesR1, R2, . . . , Rn being lower than the predetermined constant transferrate Rp, the buffer memory having a capacity Ym; wherein thepredetermined constant transfer rate Rp, a sum ΣRn of the transfer ratesR1, R2, . . . , Rn, the capacity Ym of the buffer memory, and a sum ΣSnof seek times taken by the head to move from present ones to next onesof the “n” areas of the recording medium are in a relation as follows:Ym>Rp·ΣRn·ΣSn/(Rp−ΣRn)
 21. An apparatus for recording information on arecording medium having “n” areas, where “n” denotes a predeterminednatural number equal to or greater than 2, the apparatus comprising: abuffer memory for receiving “n” information signals at transfer ratesR1, R2, . . . , Rn respectively, for temporarily storing the “n”information signals, and for outputting the “n” information signals at apredetermined constant transfer rate Rp higher than the transfer ratesR1, R2, . . . , Rn, the buffer memory having a capacity Ym; and a headfor receiving the “n” information signals from the buffer memory, andfor recording the “n” information signals on the “n” areas of therecording medium respectively on a time sharing basis and at thepredetermined constant transfer rate Rp while moving among the “n” areasof the recording medium; wherein the predetermined constant transferrate Rp, a sum ΣRn of the transfer rates R1, R2, . . . , Rn, thecapacity Ym of the buffer memory, and a sum ΣSn of seek times taken bythe head to move from present ones to next ones of the “n” areas of therecording medium are in a relation as follows: Ym>Rp·ΣRn·ΣSn/(Rp−ΣRn)22. An apparatus for recording and reproducing information on and from arecording medium having “n” areas, where “n” denotes a predeterminednatural number equal to or greater than 2, wherein at least a first areaamong the “n” areas is loaded with a first information signal among “n”information signals, the apparatus comprising: a head for reproducingthe first information signal from the first area of the recording mediumand transmitting the reproduced first information signal at apredetermined constant transfer rate Rp; and a buffer memory forreceiving the first information signal from the head at thepredetermined constant transfer rate Rp, for temporarily storing thefirst information signal, and for outputting the first informationsignal at a first transfer rate R1 lower than the predetermined constanttransfer rate Rp, the buffer memory having a capacity Ym; the buffermemory being for receiving the “n” information signals except the firstinformation signal at transfer rates R2, R3, . . . , Rn respectively,for temporarily storing the “n” information signals except the firstinformation signal, and for outputting the “n” information signalsexcept the first information signal at the predetermined constanttransfer rate Rp, the transfer rates R2, R3, . . . , Rn being lower thanthe predetermined constant transfer rate Rp; the head being forreceiving the “n” information signals except the first informationsignal from the buffer memory, and for recording the “n” informationsignals except the first information signal on the “n” areas of therecording medium except the first area at the predetermined constanttransfer rate Rp; wherein the head implements reproduction of the firstinformation signal from the first area of the recording medium andrecording of the “n” information signals except the first informationsignal on the “n” areas of the recording medium except the first area ona time sharing basis while moving among the “n” areas of the recordingmedium; and wherein the predetermined constant transfer rate Rp, a sumΣRn of the transfer rates R1, R2, . . . , Rn, the capacity Ym of thebuffer memory, and a sum ΣSn of seek times taken by the head to movefrom present ones to next ones of the “n” areas of the recording mediumare in a relation as follows: Ym>Rp·ΣRn·ΣSn/(Rp−ΣRn)
 23. An apparatusfor recording information on a recording medium having “n” areas, where“n” denotes a predetermined natural number equal to or greater than 2,the apparatus comprising: a buffer memory for receiving “n” informationsignals at transfer rates R1, R2, . . . , Rn respectively, fortemporarily storing the “n” information signals, and for outputting the“n” information signals at a predetermined constant transfer rate Rphigher than the transfer rates R1, R2, . . . , Rn; a head for receivingthe “n” information signals from the buffer memory, and for recordingthe “n” information signals on the “n” areas of the recording mediumrespectively on a time sharing basis and at the predetermined constanttransfer rate Rp while moving among the “n” areas of the recordingmedium; means for deciding whether or not parameters including thepredetermined constant transfer rate Rp, a sum ΣRn of the transfer ratesR1, R2, . . . , Rn, a sum ΣYn of sizes of the “n” information signals,and a sum ΣSn of seek times taken by the head to move from present onesto next ones of the “n” areas of the recording medium are in a relationas follows: ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn) means for, in cases where it isdecided that the parameters are in the relation, permitting the head torecord the “n” information signals on the “n” areas of the recordingmedium respectively; means for, in cases where it is decided that theparameters are not in the relation, selecting “p” information signalsfrom among the “n” information signals, where “p” denotes apredetermined natural number smaller than “n”; means for decidingwhether or not the parameters are in the relation regarding the “p”information signals; and means for, in cases where it is decided thatthe parameters are in the relation regarding the “p” informationsignals, permitting the head to record the “p” information signals on“p” areas of the recording medium respectively, the “p” areas beingamong the “n” areas of the recording medium.
 24. An apparatus forrecording information on a recording medium having “n” areas, where “n”denotes a predetermined natural number equal to or greater than 2, theapparatus comprising: a buffer memory for receiving “n” informationsignals at transfer rates R1, R2, . . . , Rn respectively, fortemporarily storing the “n” information signals, and for outputting the“n” information signals at a predetermined constant transfer rate Rphigher than the transfer rates R1, R2, . . . , Rn; a head for receivingthe “n” information signals from the buffer memory, and for recordingthe “n” information signals on the “n” areas of the recording mediumrespectively on a time sharing basis and at the predetermined constanttransfer rate Rp while moving among the “n” areas of the recordingmedium; means for deciding whether or not parameters including thepredetermined constant transfer rate Rp, a sum ΣRn of the transfer ratesR1, R2, . . . , Rn, a sum ΣYn of sizes of the “n” information signals,and a sum ΣSn of seek times taken by the head to move from present onesto next ones of the “n” areas of the recording medium are in a relationas follows: ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn) means for, in cases where it isdecided that the parameters are in the relation, permitting the head torecord the “n” information signals on the “n” areas of the recordingmedium respectively; and means for, in cases where it is decided thatthe parameters are not in the relation, controlling the head to recordthe “n” information signals on a common area in the recording medium ona time sharing basis.
 25. An apparatus as recited in claim 24, furthercomprising means for rearranging the “n” information signals into “n”rearrangement-resultant information signals in the buffer memory, andfor sequentially transmitting the “n” rearrangement-resultantinformation signals from the buffer memory to the head to sequentiallyrecord the “n” rearrangement-resultant signals.
 26. An apparatus forrecording information on a recording medium, the apparatus comprising: abuffer memory for receiving “n” information signals at transfer ratesR1, R2, . . . , Rn respectively, for temporarily storing the “n”information signals, and for outputting the “n” information signals at apredetermined constant transfer rate Rp higher than the transfer ratesR1, R2, . . . , Rn, where “n” denotes a predetermined natural numberequal to or greater than 2; a head for receiving the “n” informationsignals from the buffer memory, and for recording the “n” informationsignals on the recording medium on a time sharing basis and at thepredetermined constant transfer rate Rp; first means for causing thehead to record the “n” information signals on at least two areas in therecording medium on a time sharing basis while moving the head among theareas in the recording medium under conditions where the predeterminedconstant transfer rate Rp, a sum ΣRn of the transfer rates R1, R2 . . ., Rn, a sum ΣYn of sizes of the “n” information signals, and a sum ΣSnof seek times taken by the head to move from present ones to next onesof the areas in the recording medium are in a relation as follows:ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn) second means for causing the head to record thee“n” information signal on a common area in the recording medium on atime sharing basis; and third means for selecting and enabling one ofthe first and second means.
 27. An apparatus as recited in claim 26,wherein the third means comprises means for selecting and enabling oneof the first and second means in response to one of types of the “n”information signals, user's requirement, apparatus specifications, atype of the recording medium, and a condition of a usable area in therecording medium.
 28. An apparatus as recited in claim 14, furthercomprising means for partitioning the buffer memory into “n” areas inaccordance with values of the transfer rates R1, R2, . . . , Rn, whereinthe “n” areas in the buffer memory are assigned to the “n” informationsignals respectively.
 29. An apparatus as recited in claim 14, furthercomprising means for partitioning the buffer memory into “n” areas inaccordance with an operation mode, wherein the “n” areas in the buffermemory are assigned to the “n” information signals respectively.
 30. Aninformation-signal communication apparatus comprising the apparatus ofclaim 14 and an interface connected with the buffer memory forcommunication with an external.
 31. An information-signal recordingmedium having “n” areas on which “n” information signals are recordedrespectively, where “n” denotes a predetermined natural number equal toor greater than 2, wherein the “n” information signals can be reproducedfrom the “n” areas and can be transmitted by a head on a time sharingbasis and at a predetermined constant transfer rate Rp while the headmoves among the “n” areas of the recording medium, wherein the “n”information signals outputted from the head can be received by a buffermemory at the predetermined constant transfer rate Rp and can betemporarily stored in the buffer memory before being outputted from thebuffer memory at transfer rates R1, R2, . . . , Rn respectively, thetransfer rates R1, R2, . . . , Rn being lower than the predeterminedconstant transfer rate Rp, wherein the predetermined constant transferrate Rp, a sum ΣRn of the transfer rates R1, R2, . . . , Rn, a sum ΣYnof sizes of the “n” information signals, and a sum ΣSn of seek timestaken by the head to move from present ones to next ones of the “n”areas of the recording medium are in a relation as follows:ΣYn≧Rp·ΣRn·ΣSn/(Rp−ΣRn)
 32. An apparatus for recording and reproducinginformation on and from a recording medium having first and second areasand a management area, the management area storing managementinformation representing addresses in the first and second areas, theapparatus comprising: a first buffer memory for receiving a firstinformation signal at a first transfer rate, for temporarily storing thefirst information signal, and for outputting the first informationsignal at a predetermined constant transfer rate higher than the firsttransfer rate; a second buffer memory for receiving a second informationsignal at a second transfer rate lower than the predetermined constanttransfer rate, for temporarily storing the second information signal,and for outputting the second information signal at the predeterminedconstant transfer rate; a head for receiving the first and secondinformation signals from the first and second buffer memories andrecording the first and second information signals on the first andsecond areas of the recording medium respectively on a time sharingbasis and at the predetermined constant transfer rate while movingbetween the first and second areas of the recording medium; means forcontrolling the head to reproduce the management information from themanagement area of the recording medium before the head records thefirst and second information signals; means for deriving the addressesfrom the reproduced management information; means for searching forunoccupied regions in the first and second areas of the recording mediumin response to the derived addresses; and means for deciding whether ornot the first and second information signals can be recorded on theunoccupied regions while recording continuities related to the first andsecond information signals are maintained.
 33. An apparatus as recitedin claim 32, wherein the deciding means comprises means for decidingwhether or not the first and second information signals can be recordedon the unoccupied regions while the predetermined constant transfer rateRp, the first transfer rate Ra for the first information signal, thesecond transfer rate Rb for the second information signal, a size Ya ofthe first information signal, a size Yb of the second informationsignal, a seek time Tab taken by the head to move from the first area tothe second area of the recording medium, and a seek time Tba taken bythe head to move from the second area to the first area of the recordingmedium are in a relation as follows:(Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)
 34. An apparatus as recited inclaim 32, wherein the deciding means comprises means for decidingwhether or not the first and second information signals can be recordedon the unoccupied regions while the predetermined constant transfer rateRp, the first transfer rate Ra for the first information signal, thesecond transfer rate Rb for the second information signal, a size Ya ofthe first information signal, a size Yb of the second informationsignal, and a maximum allowable seek time Tmax taken by the head to moveon the recording medium are in a relation as follows:(Ya+Yb)≧2·Rp·(Ra+Rb)·Tmax/(Rp−Ra−Rb)
 35. An apparatus for recording andreproducing information on and from a recording medium having first andsecond areas and a management area, the first area being loaded with afirst information signal, the management area storing managementinformation representing addresses in the first and second areas, theapparatus comprising: a head for reproducing the first informationsignal from the first area of the recording medium and transmitting thereproduced first information signal at a predetermined constant transferrate; a first buffer memory for receiving the first information signalfrom the head at the predetermined constant transfer rate Rp, fortemporarily storing the first information signal, and for outputting thefirst information signal at a first transfer rate lower than thepredetermined constant transfer rate; a second buffer memory forreceiving a second information signal at a second transfer rate lowerthan the predetermined constant transfer rate, for temporarily storingthe second information signal, and for outputting the second informationsignal at the predetermined constant transfer rate; the head being forreceiving the second information signal from the second buffer memory,and for recording the second information signal on the second area ofthe recording medium at the predetermined constant transfer rate;wherein the head implements reproduction of the first information signalfrom the first area of the recording medium and recording of the secondinformation signal on the second area of the recording medium on a timesharing basis while moving between the first and second areas of therecording medium; means for controlling the head to reproduce themanagement information from the management area of the recording mediumbefore the head records the second information signal; means forderiving the addresses from the reproduced management information; meansfor searching for an unoccupied region in the second area of therecording medium in response to the derived addresses; and means fordeciding whether or not the second information signal can be recorded onthe unoccupied region-while a recording continuity related to the secondinformation signal is maintained.
 36. An apparatus as recited in claim35, wherein the deciding means comprises means for deciding whether ornot the second information signal can be recorded on the unoccupiedregion while the predetermined constant transfer rate Rp, the firsttransfer rate Ra for the first information signal, the second transferrate Rb for the second information signal, a size Ya of the firstinformation signal, a size Yb of the second information signal, a seektime Tab taken by the head to move from the first area to the secondarea of the recording medium, and a seek time Tba taken by the head tomove from the second area to the first area of the recording medium arein a relation as follows: (Ya+Yb)≧Rp·(Ra+Rb)·(Tab+Tba)/(Rp−Ra−Rb)
 37. Anapparatus as recited in claim 35, wherein the deciding means comprisesmeans for deciding whether or not the second information signal can berecorded on the unoccupied region while the predetermined constanttransfer rate Rp, the first transfer rate Ra for the first informationsignal, the second transfer rate Rb for the second information signal, asize Ya of the first information signal, a size Yb of the secondinformation signal, and a maximum allowable seek time Tmax taken by thehead to move on the recording medium are in a relation as follows:(Ya+Yb)≧2·Rp·(Ra+Rb)·Tmax/(Rp−Ra−Rb)
 38. An apparatus as recited inclaim 32, further comprising means for indicating a result of thedeciding by the deciding means.
 39. An apparatus as recited in claim 32,further comprising means for calculating a first total capacity of theunoccupied regions, means for calculating a second total capacity ofusable portions of the unoccupied regions, means for calculating anrecording efficiency equal to a ratio between the first total capacityand the second total capacity, and means for indicating the calculatedrecording efficiency.